Calculate the payback period for each of the following projects, then comment on the advisability of selection based on the payback period criterion in contrast to NPV: Project A has a cost of $15,000, returns $4,000 after-tax the first year and this amount increases by $1,000 annually over the five-year life; Project B costs $15,000 and returns $13,000 after-tax the first year, followed by four years of $2,000 per year. The firm uses a 10 percent discount rate.