Suppose a company produces a product x, and uses machines to do so. Suppose that each machine can produce 40 units, and that the company has y machines. If the company must decide how many machines to buy, as well as how much to produce, a constraint that represents this problem would be

a) XY 40

b) X + Y 40

c) X 40, Y 1

d)

X

__ 40

Y