Problem 4 A contractor is considering the following three alternatives: a. Purchase a new microcomputer system for $15,000. The system is expected to last 6 years with salvage value of $1,000. b. Lease a new microcomputer system for $3,000 per year, payable in advance. The system should last 6 years. c. Purchase a used microcomputer system for $8,200. It is expected to last 3 years with no salvage value. Use a common-multiple-of-lives approach. If MARR of 8% is used, which alternative should be selected using a discounted present worth analysis? If the MARR is 12%, which alternate should be selected