中级微观经济学范里安课件Ch.ppt

中级微观经济学21 Chapter Twenty-One Cost Curves Types of Cost Curves A total cost curve is the graph of a firm’s total cost function. A variable cost curve is the graph of a firm’s variable cost function. An average total cost curve is the graph of a firm’s average total cost function. Types of Cost Curves An average variable cost curve is the graph of a firm’s average variable cost function. An average fixed cost curve is the graph of a firm’s average fixed cost function. A marginal cost curve is the graph of a firm’s marginal cost function. Types of Cost Curves How are these cost curves related to each other? How are a firm’s long-run and short-run cost curves related? Fixed, Variable Total Cost Functions F is the total cost to a firm of its short-run fixed inputs. F, the firm’s fixed cost, does not vary with the firm’s output level. cv(y) is the total cost to a firm of its variable inputs when producing y output units. cv(y) is the firm’s variable cost function. cv(y) depends upon the levels of the fixed inputs. Fixed, Variable Total Cost Functions c(y) is the total cost of all inputs, fixed and variable, when producing y output units. c(y) is the firm’s total cost function; Av. Fixed, Av. Variable Av. Total Cost Curves The firm’s total cost function isFor y 0, the firm’s average total cost function is Av. Fixed, Av. Variable Av. Total Cost Curves What does an average fixed cost curve look like? AFC(y) is a rectangular hyperbola so its graph looks like ... Av. Fixed, Av. Variable Av. Total Cost Curves In a short-run with a fixed amount of at least one input, the Law of Diminishing (Marginal) Returns must apply, causing the firm’s average variable cost of production to increase eventually. Av. Fixed, Av. Variable Av. Total Cost Curves And ATC(y) = AFC(y) + AVC(y) Marginal Cost Function Marginal cost is the rate-of-change of variable production cost as the output level changes. That is, Marginal Cost Function The firm’s total cost function isand the fi