Afirm's are costs that increase as quantity produced increases. these costs often show illustrated by the increasingly steeper slope of the total cost curve. variable costs; diminishing marginal returns fixed costs; opportunity costs variable costs; constant returns to scale fixed costs; technological changes a firm's are costs that are incurred even if there is no output. in the short run, these costs as production increases. fixed costs; do not change variable costs; do not change variable costs; increase fixed costs; increase