2010 CFAI official mock exam

Hi, I was working on the 2010 Mock exam afternoon session problem 29. I was wondering whether there is a typo or i am just doing it the wrong way. There is a line item on the answer sheet, it is called “Increase in retained earnings”. We are using the current rate method. If you open your CFA book on page 177, it states that we have to use historical rates for retained earnings and not average rate as the answer sheet says it. I am talking about the 660 line item. I really appreciate all the comments. Thanks