Sorry I wasn't able to get back to you last night. This may be a bit late for your immediate need - your exam - but let me see if I can clear this up.
The answer is in full disjunctive normal form, which requires each variable to appear in every clause. However, this will clearly simplify to:which is also, of course, in DNF, but not full DNF because has been eliminated.
As far as your table is concerned, Moo is right: you have made an error in your working (although I'm not sure where, since you don't show it). Look at the attached diagram, where I have shown all the working. (Note: I have used , etc to denote as it's easier to type.)
You'll see that this does give the answer .