If a sum of money doubles itself in 8 years at simple interest, the ratepercent per annum is  Pick one:	A) 12	B) 12.5	C) 13	D) 13.5	E) 14

Rationale: explanation : let sum = x then simple interest = x rate = ( 100 * x ) / ( x * 8 ) = 12.5 option b
Answer: B