The Wilcox Company has two plants with the marginal cost

The Wilcox Company has two plants with the marginal cost functions
MC1 = 20 + 2Q1
MC2 = 10 + 5Q2
where MC1 is marginal cost in the first plant, MC2 is marginal cost in the second plant, Q1 is output in the first plant, and Q2 is output in the second plant.
a. If the Wilcox Company minimizes its costs and produces five units of output in the first plant, how many units of output does it produce in the second plant? Explain.
b. What is the marginal cost function for the firm as a whole?
c. Can we determine from these data the average cost function for each plant? Why or why not?