Speed of a boat in standing water is 9 kmph and the speed of the stream is 1.5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is:  Choose the correct choice from the following answers.
A) 16 hours	B) 18 hours	C) 20 hours	D) 24 hours	E) 26 hours

Rationale: "speed of upstream = 9 - 1.5 = 7.5 kmph speed of down stream = 9 + 1.5 = 10.5 kmph total time = ( 105 / 7.5 ) + ( 105 / 10.5 ) = 24 hrs answer : d"
Answer: D