A lent Rs. 5000 to B for 2 years and Rs. 3000 to C for 4 years on simple interest at the same rate of interest and received Rs. 3300 in all from both of them as interest. The rate of interest per annum is?  Select the correct option.
A) 16 % B) 12 % C) 74 % D) 10 % E) 15 %

Rationale: "let the rate be r % p . a . then , ( 5000 * r * 2 ) / 100 + ( 3000 * r * 4 ) / 100 = 3300 100 r + 120 r = 3300 r = 15 % answer : e"
Answer: E