Aretailer has determined that the cost c of
ordering and storing x units of a product is
c=6x+9/x
(a) write the expression for cost as a single fraction.
(b) determine the cost for ordering and storing - x=240
units of this product.

A. The expression given in the question is

c = 6x + (900000/x)
c = (6x^ +900000)/x
I hope that this is the expression that you were looking for.

b. When x = 240, then

c = [6 * (240)^2 + 900000]/ 240
   = (6 * 57600) + 900000/240
   = (345600 + 900000)/240
   = 5190

From the above deduction, it can be concluded that the cost of ordering and storing is 5190. I hope the procedure is clear enough for you to understand.