A sum fetched a total simple interest of Rs. 100 at the rate of 5 p.c.p.a. in 4 years. What is the sum? Choose the correct option
A) 800 B) 600 C) 500 D) 1000 E) 300

Rationale: "sol . principal = rs . [ 100 * 100 / 5 * 4 ] = rs . [ 10000 / 20 ] = rs . 500 . answer c"
Answer: C