two brands of a protective coating are being considered.
brand A costs 15.80 per gallon.
Past experience with Brand A has revealed that it will cover 350 square feet of surface per gallon,will give satisfactory service for 3 years, and can be applied at the rate of 70 square feet per hour.
Brand B, which costs 20.40 per gallon, is estimated to cover 400 square feet of surface per gallon and can be applied at the rate of 80 square feet per hour.
the wage rate of the worker is 17 per hour.
if an interest rate of 10% is used, how long should Brand B last to provide service at equal cost with that provided by Brand A?