曼昆经济学原理英文版文案加习题答案13章.doc

Chapter 13/The Costs of Production23913THE COSTS OF PRODUCTIONWHATS NEW IN THE SEVENTH EDITION:There are no major changes to this chapter.LEARNING OBJECTIVES:By the end of this chapter, students should understand:what items are included in a firms costs of production.the link between a firms production process and its total costs.the meaning of average total cost and marginal cost and how they are related.the shape of a typical firms cost curves.the relationship between short-run and long-run costs.CONTEXT AND PURPOSE:Chapter 13 is the first chapter in a five-chapter sequence dealing with firm behavior and the organization of industry. It is important that students become comfortable with the material in Chapter 13 because Chapters 14 through 17 are based on the concepts developed in Chapter 13. To be more specific, Chapter 13 develops the cost curves on which firm behavior is based. The remaining chapters in this section (Chapters 14-17) utilize these cost curves to develop the behavior of firms in a variety of different market structurescompetitive, monopolistic, monopolistically competitive, and oligopolistic. The purpose of Chapter 13 is to address the costs of production and develop the firms cost curves. These cost curves underlie the firms supply curve. In previous chapters, we summarized the firms production decisions by starting with the supply curve. While this is suitable for answering many questions, it is now necessary to address the costs that underlie the supply curve in order to address the part of economics known as industrial organizationthe study of how firms decisions about prices and quantities depend on the market conditions they face.KEY POINTS:The goal of firms is to maximize profit, which equals total revenue minus total cost.When analyzing a firms behavior, it is important to include all the opportunity costs of production. Some of the opportunity costs, such as the wages a firm pays its workers, are explicit. Other opportunity costs, such as the wages the firm owner gives up by working at the firm rather than taking another job, are implicit. Economic profit takes both explicit and implicit costs into account, whereas accounting profits consider only explicit costs.A firms costs reflect its production process. A typical firms production function gets flatter as the quantity of an input increases, displaying the property of diminishing marginal product. As a result, a firms total-cost curve gets steeper as the quantity produced rises.A firms total costs can be divided between fixed costs and variable costs. Fixed costs are costs that do not change when the firm alters the quantity of output produced. Variable costs are costs that change when the firm alters the quantity of output produced.From a firms total cost, two related measures of cost are derived. Average total cost is total cost divided by the quantity of output. Marginal cost is the amount by which total cost rises if output increases by one unit.When analyzing firm behavior, it is often useful to graph average total cost and marginal cost. For a typical firm, marginal cost rises with the quantity of output. Average total cost first falls as output increases and then rises as output increases further. The marginal-cost curve always crosses the average-total-cost curve at the minimum of average total cost.A firms costs often depend on the time horizon considered. In particular, many costs are fixed in the short run but variable in the long run. As a result, when the firm changes its level of production, average total cost may rise more in the short run than in the long run.CHAPTER OUTLINE:This is an extremely important chapter, and it is critical that students have an understanding of the important principles developed here in order to follow the material presented in the next several chapters. Do not be surprised at the number of students who are unfamiliar with such seemingly simple concepts as revenue, costs, and profits.I.What Are Costs?Point out to students that it is possible for firm owners to have different goals, but the one motive that makes the most accurate prediction about how firm managers behave is the assumption of profit maximization. To help illustrate this sometimes-controversial assumption, use the analogy of an automobile driver. Ask students to name an assumption about the goal of most drivers. Most would agree that drivers behave as if their goal is to get from one place to another in the least amount of time. This may not explain the behavior of every driver (i.e., “Sunday” drivers), but it works for most.A.Total Revenue, Total Cost, and Profit1.The goal of a firm is to maximize profit.2.Definition of total revenue: the amount a firm receives for the sale of its output.Students rarely have trouble understanding the concept of explicit costs. However, they do often have difficulty understanding the nature of implicit costs. Make sure that they grasp the concept here, because it is important in understanding why firms continue to operate even if they are earning zero economic profit in the long run.3.Definition of total cost: the market value of the inputs a firm uses in production.4.Definition of profit: total revenue minus total cost.B.Costs as Opportunity Costs1.Principle #2: The cost of something is what you give up to get it.2.The costs of producing an item must include all of the opportunity costs of inputs used in production.3.Total opportunity costs include both implicit and explicit costs.a.Definition of explicit costs: input costs that require an outlay of money by the firm.b.Definition of implicit costs: input costs that do not require an outlay of money by the firm.c.The total cost of a business is the sum of explicit costs and implicit costs.d.This is the major way in which accountants and economists differ in analyzing the performance of a business.e.Accountants focus on explicit costs, while economists examine both explicit and implicit costs.C.The Cost of Capital as an Opportunity Cost1.The opportunity cost of financial capital is an important cost to include in any analysis of firm performance.2.Example: Caroline uses $300,000 of her savings to start her firm. It was in a savings account paying 5% interest.3.Because Caroline could have earned $15,000 per year on this savings, we must include this opportunity cost. (Note that an accountant would not count this $15,000 as part of the firms costs.)4.If Caroline had instead borrowed $200,000 from a bank and used $100,000 from her savings, the opportunity cost would not change if the interest rate stayed the same (according to the economist). But the accountant would now count the $10,000 in interest paid for the bank loan.D.Economic Profit versus Accounting ProfitFigure 11.Figure 1 highlights the differences in the ways in which economists and accountants calculate profit.2.Definition of economic profit: total revenue minus total cost, including both explicit and implicit costs.a.Economic profit is what motivates firms to supply goods and services.b.To understand how industries evolve, we need to examine economic profit.3.Definition of accounting profit: total revenue minus total explicit cost.4.If implicit costs are greater than zero, accounting profit will always exceed economic profit.II.Production and CostsYou may want to give students a handout that summarizes the definitions and provides them an opportunity to practice the calculations in this chapter. (See the alternative classroom examples.)A.The Production Function1.Definition of production function: the relationship between quantity of inputs used to make a good and the quantity of output of that good.It will be beneficial at this point to distinguish between the long run and the short run. This will help students understand the distinction between fixed inputs and variable inputs.2.Example: Carolines cookie factory. The size of the factory is assumed to be fixed; Caroline can vary her output (cookies) only by varying the labor used.Table 1Number of WorkersOutputMarginal Product of LaborCost of FactoryCost of WorkersTotal Cost of Inputs00-$30$0$30150503010402904030205031203030306041402030407051501030508061555306090Go through this table, column by column. Make sure that students understand the calculations involved. 3.Definition of marginal product: the increase in output that arises from an additional unit of input.a.As the amount of labor used increases, the marginal product of labor falls.b.Definition of diminishing marginal product: the property whereby the marginal product of an input declines as the quantity of the input increases.Point out that diminishing marginal returns is a result of fixed inputs and, therefore is a short-run phenomenon.ALTERNATIVE CLASSROOM EXAMPLE:Consider the short-run production of a small firm that makes sweaters. These sweaters are made using a combination of labor and knitting machines. In the short run, the firm has signed a lease to rent one machine. Therefore, in the short run, the firm cannot vary the amount of knitting machines it uses. However, the firm can vary the amount of labor it employs.The first two columns in the table below show the production level that the firm can achieve at various amounts of labor:Labor (# workers)Total OutputMarginal Product00-14421063133415251614.We can draw a graph of the firms production function by plotting the level of labor (x-axis) against the level of output (y-axis).Figure 2a.The slope of the production function measures marginal product. b.Diminishing marginal product can be seen from the fact that the slope falls as the amount of labor used increases.B.From the Production Function to the Total-Cost Curve1.We can draw a graph of the firms total cost curve by plotting the level of output (x-axis) against the total cost of producing that output (y-axis).a.The total cost curve gets steeper and steeper as output rises.b.This increase in the slope of the total cost curve is also due to diminishing marginal product: As Caroline increases the production of cookies, her kitchen becomes overcrowded, and she needs a lot more labor.Activity 1Growing Rice on a ChalkboardType:In-class demonstrationTopics: Diminishing returns and increasing costsMaterials needed: Chalkboard and chalk Time: 25 minutesClass limitations: Works in classes with more than 15 studentsPurposeStudents often have difficulty understanding why diminishing returns exist in short-run production. This activity vividly demonstrates how fixed factors constrain the returns to variable inputs. Then the cause of increasing marginal cost is obvious.InstructionsPrepare the game by selecting two volunteers and outlining two rectangular areas on the chalkboard, approximately 2 3 feet. Next to each area, label a column “Labor” and another “Total Output.” Give each volunteer one piece of chalk and hide any other pieces. The chalk is a fixed factor of production.The volunteers are farmers and the outlined areas are their farm fields. They produce rice by writing the word “RICE” in large letters inside their own field. The letters need to be at least three inches high. They want to produce as much rice as possible in each 15-second time period.The variable input in this example is labor. The game is played repeatedly, adding another student each period. Eventually five students will be crowded around each “field” trying to write with a tiny piece of chalk. The constraints from the fixed factors are physically demonstrated.Start the game with zeros in both the labor and total output columns; with no labor, no rice is produced. Then have the two volunteers race to see how much they can produce in 15 seconds. Record their production under “Total Output” with one “Labor.” III.The Various Measures of CostA.Example: Conrads Coffee ShopTable 2OutputTotal CostFixed CostVariable CostAverage Fixed CostAverage Variable CostAverage Total CostMarginal Cost0 $3.00 $3.00 $0-13.303.000.30$3.00$0.30$3.30$0.3023.803.000.801.500.401.900.5034.503.001.501.000.501.500.7045.403.002.400.750.601.350.9056.503.003.500.600.701.301.1067.803.004.800.500.801.301.3079.303.006.300.430.901.331.50811.003.008.000.381.001.381.70912.903.009.900.331.101.431.901015.003.0012.000.301.201.502.10Figure 3ALTERNATIVE CLASSROOM EXAMPLE:Consider the sweater manufacturer (described earlier). The firm is currently renting one machine for $25 per day. Each worker is also paid $25 per day.LaborOutputFixed CostVariable CostTotal CostAverage Fixed CostAverage Variable CostAverage Total CostMarginal Cost00$25$0$25-14252550 $6.25 $6.25$12.50 $6.252102550752.505.007.504.1731325751001.925.777.698.33415251001251.676.678.3312.50516251251501.567.819.3825.00B.Fixed and Variable Costs1.Definition of fixed costs: costs that do not vary with the quantity of output produced.2.Definition of variable costs: costs that do vary with the quantity of output produced.3.Total cost is equal to fixed cost plus variable cost.C.Average and Marginal Cost1.Definition of average total cost: total cost divided by the quantity of output.2.Definition of average fixed cost: fixed costs divided by the quantity of output.3.Definition of average variable cost: variable costs divided by the quantity of output.4.Definition of marginal cost: the increase in total cost that arises from an extra unit of production.5.Average total cost tells us the cost of a typical unit of output and marginal cost tells us the cost of an additional unit of output.D.Cost Curves and Their ShapesFigure 41.Rising Marginal Costa.This occurs because of diminishing marginal product.b.At a low level of output, there are few workers and a lot of idle equipment. But as output increases, the coffee shop gets crowded and the cost of producing another unit of output becomes high.2.U-Shaped Average Total