Problem: a person lent a certain sum of money at 5 % per annum at simple interest and in 8 years the interest amounted to $ 420 less than the sum lent . what was the sum lent ?
Rationale: "p - 420 = ( p * 5 * 8 ) / 100 p = 700 the answer is c ."
annotated_formula: divide(420, subtract(const_1, divide(multiply(5, 8), const_100)))