Answer: b. $40
Explanation:
A firm maximises its profits where Marginal Revenue equals marginal cost.
Marginal revenue is the additional revenue gained by selling one more unit of production.
At 40 units, the marginal revenue is equal to;
= Total revenue at 40 units - total revenue at 30 units
= ( 7 * 40) - ( 8 * 30)
= 280 - 240
= $40
At 40 units the marginal cost is;
= total cost at 40 units - total cost at 30 units
= 170 - 130
= $40
MR=MC which is $40.
