I have a double degree in Mathematics and Physics. I have taken several courses in which Fourier Series in particular have either been used heavily, or have been the main topic of discussion.
In order to get a more accurate estimate of how long this will actually take me, I would need to get a better feel for the extend and requirements of your project (do you have a prompt for it?). So, I have put 3 days and $111 as placeholders, though I do not expect that it should take any longer (or cost any more) than that.
Let me know if you have any questions for me. I am here to help :)