$600 will become $720 in 4 years find the rate of interest?	Choose the correct choice from the following answers:	A) 10 %	B) 15 %	C) 5 %	D) 7 %	E) 20 %

Rationale: "si = simple interest = a - p = 720 - 600 = $ 120 r = 100 si / pt = 100 * 120 / 600 * 4 = 5 % answer is c"
Answer: C