30. To make a batch of 1,000 units of a certain item, it is estimated that 120 direct labor hours are required at a cost of $10/hour. Direct material costs are estimated at $1,500 per batch. The overhead costs are calculated based on an overhead rate of $7.50 per direct labor hour. The item can be readily purchased from a local vendor for $4 per unit.

a. Should the item be made or purchased?

b. Over what range of overhead rate is your answer in Part a valid?