As a part of my post-doctoral project, I am working on some problem. Apart from my post-doc mentor, another junior member had been added to the project to assist me and been given the position of ``Junior Research Fellow'' (JRF). Initially, I thought that a proper person who would be able to learn the methods of my field would be chosen to do the job but the person X was chosen who is from a different background. I still hoped that X would learn at least basic things (which are not very difficult) and would be able to help me. However, X kept telling me that they want time to learn and in my frank opinion, never tried even a bit to learn anything.
In the meantime, I gave a very simple work to X : Download around 150 data-files from the Internet and name them as I want. Even this took long time but this is the only thing that X has done during the whole year.
On the other hand, I studied the whole problem, did literature survey, discussed with various experts in the filed, found a proper way to solve the problem and built 3 complex codes to work things out. Now we have nice results which can be published in my opinion. Now my mentor tells me to add X as the second author of our paper. I am quite unhappy with this and I expressed my opinion to the mentor. But according to the mentor, we must add X because we must show funding agency that everybody worked together. I am surprised at this and hence I am asking whether this is really normal and how should I handle the situation.