A product can be produced using either of two machines. The first machine costs $25.00 to set up to begin production; the second costs $5.00. The first machine can produce the product at a cost of S1.00 each, and the second machine can produce the product at a cost of S4.00 each. If 15 products are to be made and you wish to minimize cost, then .

a. the first machine should be used

b. the second machine should be used

c. either machine can be used

d. the product should not be produced