NCEES 2001 Exam - #507

Could anyone provide a better solution and explanation to this problem than what they provide in the book?

I got the wrong answer because I multiplied the mass flow rate of the air stream by the inlet & outlet humidity ratios and kept the mass flow rate of water stream stay constant.
 

I guess I should have not multiplied the air flow rates by the humidity ratios and instead removed the mass rate of evaporation from the mass flow rate of water. 

Do you have the answer or the solution...  I fell smack dad in the middle of two answers.  Which means I probably did the whole thing wrong.

Nevermind...i have it

Answer is B. I can post their solution if needed. 

I figured their method out last night.  I just wanted to put it in MathCad.