The Internal Revenue Service (IRS) has determined that during each of the next 12 months it will need the numbers of supercomputers given in the file P04_88.xlsx. To meet these requirements, the IRS rents supercomputers for a period of one, two, or three months. It costs $1000 to rent a supercomputer for one month, $1800 for two months, and $2500 for three months. At the beginning of month 1, the IRS has no supercomputers.

a. Determine the rental plan that meets the requirements for the next 12 months at minimum cost. You can assume that fractional rentals are allowed. Thus, if your solution says to rent 140.6 computers for one month, you can round this up to 141 or down to 140 without much effect on the total cost.

b. Suppose the monthly requirement increases anywhere from 10% to 50% each month. (Assume that whatever the percentage increase is, it is the same each month.) Use SolverTable to see whether the total rental cost increases by this same percentage.