perry and susan williams just retired, moved to the lake and purchased fishing equipment and a bass boat for perry's new fishing business. the total investment is 25,200 - the cost of the equipment and boat. susan told perry he needed to earn at least 10 percent return per year, because their retirement investment portfolio had averaged this amount over the years. surprisingly, and as a result of their investment in the equipment, they have actually been able to sell some of their catch to local restaurants at the marina. they have had positive cash flow, in excess of expenses, of $5000,$5500,$10000,$15000 over a four year period, respectivaly. at the end of their forth year at the lake, they finally decide to really retire. the Williams sell all of their equipment to some local college students for $3000, what is the NPV of the business? the answer is 3698.30, but how do you solve for this using excel. also what is the IRR on there investment in the business? the answer is 15.27, but how to solve for this using excel? thanks