Find and interpret the marginal cost with respect to x if

Question

Question: The joint cost (in dollars) for products X and Y is given by

C(x, y) = 40 + 3x² + y² + xy

where x represents the quantity of X and y represents the quantity of Y.

(a) Find and interpret the marginal cost with respect to x if 20 units of product X and 15 units of product Y are produced.

(b) Find and interpret the marginal cost with respect to y if 20 units of X and 15 units of Y are produced.