If a sum of money doubles itself in 10 years at simple interest, the ratepercent per annum is	Choose the correct choice.
A) 10
B) 12.5
C) 13
D) 13.5
E) 14

Rationale: "explanation : let sum = x then simple interest = x rate = ( 100 * x ) / ( x * 10 ) = 10 option a"
Answer: A