if a lends rs . 3500 to b at 10 % per annum and b lends the same sum to c at 15 % per annum then the gain of b in a period of 3 years is ?
"( 3500 * 5 * 3 ) / 100 = > 525 answer : a"
subtract(divide(multiply(multiply(3500, 15), 3), const_100), divide(multiply(multiply(3500, 10), 3), const_100))