On a purchase of $110, a store offered a payment plan consisting of a $10 down payment and 12 monthly payments of $10 each. What percent of the purchase price, to the nearest tenth of a percent, did the customer pay in interest by using this plan?	Pick one:
A) 9.5 %
B) 10.5 %
C) 11.5 %
D) 9.1 %
E) 12.5 %

Rationale: "12 * 10 + 10 = 130 ( 10 / 110 ) * 100 = 9.1 answer : d"
Answer: D