After mining 9,273 tons of coal, Blue Sky Minings managers note that the marginal cost of mining

Question:

After mining 9,273 tons of coal, Blue Sky Mining’s managers note that the marginal cost of mining the next ton of coal would be $40 per ton. They also calculate that the user cost of mining that next ton of coal would be $35. If the market price of coal is $72, should Blue Sky mine an additional ton of coal?

a. Yes.

b. No.

c. More information is needed.