An uncovered swimming pool loses 1 inch of water off its 1,000ft^2 surface each week due to evaporation. the heat of vaporization for water at the pool temperature is 1,050 Btu/lb. the cost of energy to heat the pool is $10.00 per million Btu. a salesman claims that a $500 pool cover that reduces evaporizative losses by two-thirds will pay for itself in one 15-week swimming season. can it be true?