The cost price of an book is 64% of the marked price. Calculate the gain percent after allowing a discount of 13%?  Choose the most appropriate option:	A) 31.5%	B) 35.9%	C) 37.5%	D) 39.5%	E) 30.5%
Let marked price = $100.   Then, C.P. = $64, S.P. = $87   Gain % = 23/64 * 100 = 35.9%. 35.9%
<result>B</result>
The cost price of an book is 64% of the marked price. Calculate the gain percent after allowing a discount of 13%?