A firm is evaluating two projects X and Z. Project X has an initial investment of $80,000 and cash inflows at the end of each of the next five years of $25,000. Project Z has a initial investment of $120,000 and cash inflows at the end of each of the next five years of $40,000. Assume the cost of capital of 10%. Which project(s) should the firm accept if

a) projects X and Z are independent?

b) projects X and Z are mutually exclusive?