A sum was put at simple interest at a certain rate for 4 years Had it been put at 2% higher rate, it would have fetched 56 more. Find the sum.  Pick one: A) 500 B) 600 C) 700 D) 800 E) none of these

Rationale: "difference in s . i . = p × t / 100 ( r 1 − r 2 ) ⇒ 56 = p × 4 × 2 / 100 ( ∵ r 1 - r 2 = 2 ) ⇒ p = 56 × 100 / 4 × 2 = 700 answer c"
Answer: C