If X is invested in a bank at a rate of simple interest of y% p.a. for two years, then the interest earned is 500. if X is invested at y% p.a., for two years when the interest is compounded annually, the interest is 512.50. What is the value of X? Choose the correct answer:
A) 8000 B) 6000 C) 5000 D) 4000 E) 3000

Rationale: "simple way to solve this question is to use options . from si , we know that x * y = 25,000 . now , put the value of x = 5000 , we will have y = 5 % to calculate ci , now , we know 1 st year amount = 5000 + 5 % of 5000 = 5250 . 2 nd year , amount = 5250 + 5 % of 5250 = 5512.50 . we can see after 2 years interest = 5512.50 - 5000 = 512.50 hence , it satisfies the question . hence c is the correct answer"
Answer: C