Present sales amount to $7,700$ units per month. An order has been received from a customer in a foreign market for $1,400$ units. The order would not affect regular sales. Total fixed costs, both manufacturing and selling and administrative, would not be affected by this order. The variable selling and administrative costs would have to be incurred for this special order as well as all other sales. Assume that direct labor is a variable cost.

Assume the company has $70$ units left over from last year which have small defects and which will have to be sold at a reduced price for scrap. The sale of these defective units will have no effect on the company's other sales. Which of the following costs is relevant in this decision?