Problem: find the cost of fencing around a circular field of diameter 12 m at the rate of rs . 3.50 a meter ?
Rationale: "2 * 22 / 7 * 6 = 37.7 37.7 * 3 1 / 2 = rs . 131.95 answer : a"
annotated_formula: multiply(circumface(divide(12, const_2)), 3.50)