Basics of Engineering Economy 2nd Edition by Anthony Tarquin,Leland Blank

Exercise 9

A University of Massachusetts study found that married women who work outside the home do about one hour less of housework per week for every $7500 they earn outside the home. Assume that they hire a housekeeper one time per week for $120; that the $7500 is received in uniform amounts of $625 per month; and, that the housekeeper is paid weekly with these payments made before the $625 is received. What rate of return are they making per week on their "investment" in the housekeeper