The Below Figure Shows the Various Combinations of the Goods

The below figure shows the various combinations of the goods X and Y that yield different levels of utility.Figure 7.3

-A firm's marginal cost equals the:

A) ratio of total cost to total quantity.
B) slope of the demand curve under perfect competition.
C) slope of the total product curve when the latter is at its maximum.
D) change in total cost divided by the change in total output.
E) slope of the supply curve.