If a - b = 10 and a2 + b2 = 210, find the value of ab.  Select.
A) 68	B) 42	C) 55	D) 18	E) 44
2ab = (a2 + b2) - (a - b)2   = 210 - 100= 
<gadget id="calculator">210 - 100</gadget>
<output>110</output>
110   ab= 55.   Answer: 55
<result>C</result>
If a - b = 10 and a2 + b2 = 210, find the value of ab.