A firm has the following total cost function TC = 0.8Q3- 20Q2+ 220Q + 500
(a) What is the average total cost if output is 15 units?
(b) At what level of output the average cost is minimum?
(c) At what level(s) of output(s) the marginal cost is 100?
(d) At what level of output the marginal cost is the same as the average fixed cost?
(e) At what level of output the difference between the average total cost and the average variable cost is 50?
(f) At what level of output the difference between the average total cost and the average fixed cost is 100?