A sum was put at simple interest at a certain rate for 10 years . Had it been put at 5% higher rate , it would have fetched Rs.100 more. What was the Sum?  Choose the correct choice from the following options.
A) s . 350
B) s . 700
C) s . 200
D) s . 600
E) s . 500

Rationale: "at 5 % more rate , the increase in s . i for 10 years = rs . 100 ( given ) so , at 5 % more rate , the increase in si for 1 year = 100 / 10 = rs . 10 / - i . e . rs . 10 is 5 % of the invested sum so , 1 % of the invested sum = 10 / 5 therefore , the invested sum = 10 × 100 / 5 = rs . 200 answer : c"
Answer: C