Joe invested a certain sum of money in a simple interest bond whose value grew to $560 at the end of 3 years and to $660 at the end of another 5 years. What was the rate of interest in which he invested his sum?	Choose the correct answer:
A) 3%  B) 4%  C) 5%  D) 6%  E) 7%
In 5 years, the value grew $100, so the simple interest was $20 per year.   In 3 years, the total interest was 3*$20 = $60   The principal is $560 - $60 3* 20= 
<gadget id="calculator">3* 20</gadget>
<output>60</output>
$60   The principal is $560 - $60 = 500.   The interest rate is $20/$500 560 -  60= 
<gadget id="calculator">560 -  60</gadget>
<output>500</output>
500.   The interest rate is $20/$500= 4%   The answer is 4%.
<result>B</result>
Joe invested a certain sum of money in a simple interest bond whose value grew to $560 at the end of 3 years and to $660 at the end of another 5 years. What was the rate of interest in which he invested his sum?