Okay, so I got the first part however I did the next half of the problem a little different and dont understand why my answer is incorrect.
The book does it like this:
50K(1+(P/F,10%,2) + 20K(P/A,10%,4) - 10K(P/A,10%,2) = 137K
I did this:
50K(1+(P/F,10%,2) + 10K(P/A,10%,2) + 20K(P/A,10%,2) =...