If a - b = 3 and a^2 + b^2 = 29, find the value of ab.
Choose the correct choice from the following:
A) 12  B) 15  C) 10  D) 18  E) 13
2ab = (a^2 + b^2) - (a - b)^2   = 29 - 9= 
<gadget id="calculator">29 - 9</gadget>
<output>20</output>
20   ab= 10.   Answer is 10.
<result>C</result>
If a - b = 3 and a^2 + b^2 = 29, find the value of ab.