The oil burner in a certain house is used to heat the house and to heat the hot water. During the seven cold months when the house is heated, an average of 200 gallons of oil a month is used. In the remaining 5 months, when the house is not heated, a total of 200 gallons of oil is used. What percentage of the year's oil supply is required to heat water during these five months?
a) 1/8 %
b) 7 %
c) 12 1/2 %
d) 14 %
