At what rate percent per annum will the simple interest on a sum of money be 4/5 of the amount in 10 years? Choose the correct choice from the following answers:
A) 4 %
B) 7 %
C) 8 %
D) 3 %
E) 1 %

Rationale: "let sum = x . then , s . i . = 4 x / 5 , time = 10 years . rate = ( 100 * 4 x ) / ( x * 5 * 10 ) = 8 % answer : c"
Answer: C