To make an item in-house, equipment costing $250,000 must be purchased. It will have a life of 4 years, an annual cost of $80,000, and each unit will cost $40 to manufacture. Buying the item externally will cost $100 per unit. At i = 15% per year, it is cheaper to make the item in-house if the number per year needed is:
(a) Above 1047 units
(b) Above 2793 units
(c) Equal to 2793 units
(d) Below 2793 units