A certain sum is invested at simple interest at 18% p.a. for two years instead of investing at 12% p.a. for the same time period. Therefore the interest received is more by Rs. 600. Find the sum? Choose the correct answer:
A) 7000  B) 7029  C) 2778  D) 2800  E) 5000

Rationale: "let the sum be rs . x . ( x * 18 * 2 ) / 100 - ( x * 12 * 2 ) / 100 = 600 = > 36 x / 100 - 24 x / 100 = 600 = > 12 x / 100 = 600 = > x = 5000 . answer : e"
Answer: E