Problerms 55 4-82 A contractor estimates maintenance costs for a new backhoe to be $500 for the first month with a monthly increase of 0.75%. The contractor can buy a 4-year maintenance contract for $20,000 at any point. If the contract is purchased at the same time as the backhoe is purchased, the dealer has offered a 10% discount. Use 1-1 % per month. What should the contractor do? Contributed by Hamed Kashani, Saeid Sadri, and aabak Ashuri, Georgia Institute of Technology