Find the cost of fencing around a circular field of diameter 42 m at the rate of Rs.3 a meter?
Choices:
A) 138 B) 390 C) 393 D) 279 E) 222

Rationale: "2 * 22 / 7 * 21 = 131 131 * 3 = rs . 393 answer : c"
Answer: C