I sold a book at a profit of 10%. Had I sold it for $120 more, 15% would have been gained. Find the cost price?	Pick one:
A) $2000 B) $2500 C) $2400 D) $3120 E) $1540
115% of cost - 110% of cost = $120   5% of cost = $120   cost = 120*100/5= 
<gadget id="calculator">120*100/5</gadget>
<output>2_400</output>
$2400   Answer is $2400
<result>C</result>
I sold a book at a profit of 10%. Had I sold it for $120 more, 15% would have been gained. Find the cost price?