I am currently working on a letter and I wrote a sentence similar to this:
I created my own goals, which, together with my studies in mathematics, has given me an excellent foundation for this program.
I believe this is a correct sentence, but my friend claims it has a plural subject. I believe that "my own goals" constitutes a singular set, so "has" is correct. My friend argues two things: "my own goals" is plural and "together with…" makes a compound subject. I disagree on the first because I am considering the whole, not the parts, and I disagree with the latter because it is not part of the subject. It is a dependent clause just to point out the fact that this isn't the only reason I have an excellent foundation for the program. While I believe one could treat "my own goals" as a plural group rather than a singular set, I think the compound subject argument is completely false. I thought about replacing "together" with "along" because it may be less likely to cause people to think this is a compound subject.
Which is correct? Which do you think is better and why?