Fixed. Variable total cost functions F is the total cost to a firm of its short- run fixed inputs(固定投入).F,the firm's fixed cost, does not vary with the firm' s output level Cly) is the total cost to a firm of its variable inputs(可变投入)when producing y output units. Cyy)is the firm's variable cost function Cyy) depends upon the levels of the fixed inputs.Fixed, Variable & Total Cost Functions F is the total cost to a firm of its short￾run fixed inputs （固定投入）. 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 （可变投入）when producing y output units. cv (y) is the firm’s variable cost function. cv (y) depends upon the levels of the fixed inputs