For the following total cost function, find the marginal cost (MC), average total cost (ATC), and average variable cost (AVC), and then decide which of the following are true: TC = 0.1Q^3 - 4Q^2 + 80Q + 150 a. MC = 0.3Q^2 - 8Q + 80 b. ATC = 0.1Q^2 - 4Q + 80 c. AVC = 0.1Q^2 - 4Q + 80 d. MC=AVC at Q=20