单选题
The following equations have been developed for a company:
| Demand curve | P=150-5×Q |
| Total revenue curve | TR=150×Q-5×Q2 |
| Marginal revenue curve | MR=150-10×Q |
| Total cost curve | TC=Q3-10×Q2+73×Q+120 |
| Average cost curve | AC=Q2-10×Q+73+120/Q |
| Marginal cost curve | MC=3×Q2-20×Q+73 |
| P: price per unit Q cost per unit | |
The profit maximizing output for this firm (in units) is closest to:
【正确答案】
A
【答案解析】
A is correct. The profit-maximizing output will arise when MR = MC.
MR = 150-10×Q= MC= 3 × Q2 -20×Q+ 73.
On reduction, this becomes: 3 × Q2 －10 × Q- 77 = 0.
Only with Q = 7 will this equation be satisfied: 3 × 72 - 10 × 7 - 77 = 0.
Alternatively, net profit under each alternative can be compared:
