on a purchase of $ 127 , a store offered a payment plan consisting of a $ 27 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 ?
"12 * 10 + 27 = 147 ( 27 / 127 ) * 100 = 21.3 answer : c"
multiply(divide(subtract(add(multiply(10, 12), 27), multiply(10, 12)), 127), const_100)