Wachman Company produces a product with the following per-unit costs:

Direct materials $15 Direct labor 6 Manufacturing overhead 10 Last year, Wachman produced and sold 1,000 units at a price of $75 each. Total selling and administrative expense was $30,000.

Conversion cost per unit was:

a. $15.

b. $21.

c. $31.

d. $16.

e. none of the above.