The joint cost (in dollars) for two products is given by C(x, y) = 33 + x2 + 3y+ 2xy where x represents the quantity of product X produced and y represents the quantity of product Y produced. (a) Find the marginal cost with respect to x if 6 units of product X and 12 units of product Y are produced. $ d Interpret your answer. O If x remains at 12, the expected change in cost for a 7th unit of y is this amount. O If y remains at 12, the expected change in cost for a 7th unit of x is this amount. O If y remains at 6, the expected change in cost for a 13th unit of x is this amount. O If x remains at 6, the expected change in cost for a 13th unit of y is this amount. (b) Find the marginal cost with respect to y if 6 units of product X and 12 units of product Y are produced. $ Interpret your answer. O If x remains at 12, the expected change in cost for a 7th unit of y is this amount. If y remains at 6, the expected change in cost for a 13th unit of x is this amount. If y remains at 12, the expected change in cost for a 7th unit of x is this amount. O If x remains at 6, the expected change in cost for a 13th unit of y is this amount