A firm sells 1000 units per week. It charges $15 per unit, the average variable costs are $10, and the average costs are $25. In the long run, the firm should a. ​Shut-down because it is cost effective to pay off the remaining fixed costs b. ​Continue operating as the firm is covering all the variable costs and some of the fixed costs c. ​Shut-down as the firm is making a loss of $10,000 per week d. ​Shut-down as price is lower than average cost