schweser practice exam vol 1 exam 2 Q#1 IPS available, determine, therefore

Bluetick1010

Hi there
I just did this question on a personal IPS for a family. In the case in briefly mentions the family wants to pay for their kids educations (it gives the ages). SO i took an estimate of $150K per kid and present value at 7% to come up will a ball park estimate (about $200K total). I then subtracted this from their savings to determine to get the amount available which they would need to draw an income from.
The answers in Schweser do not do this - therefore my estimate of furture needs is slightly higher. I do not think what i did was incorrect - but was only being conservative given the information.
My question is - would this be marked wrong on an actual exam or are the markers trained to account for this type of thinking?
Thanks