If the simple interest on $2000 increase by $40,when the time increase by 4 years. Find the rate percent per annum.	Select the correct option
A) 1.2 % B) 0.5 % C) 0.7 % D) 0.9 % E) 0.3 %

Rationale: "applying the above formula , we have 40 = 2000 * r * 4 / 100 r = 40 * 100 / 2000 * 4 = 0.5 % . answer is b"
Answer: B