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. 1980 in all from both of them as interest. The rate of interest per annum is? Choose the correct choice from the following:
A) 16 %
B) 12 %
C) 9 %
D) 10 %
E) 45 %

Rationale: "let the rate be r % p . a . then , ( 5000 * r * 2 ) / 100 + ( 3000 * r * 4 ) / 100 = 1980 100 r + 120 r = 1980 r = 9 % answer : c"
Answer: C