How do I increase utorrent upload speed?

I am sending a file to a friend via utorrent. My friend’s download speed is at around 100–200 kb/s when downloading files with a lot of people seeding, but when I seed a file he gets it at the speed of only 20–30 kb/s. My speed is pretty good, so the problem is not with my speed. I made a private .torrent file as I don’t want somebody else to be able to receive the file. Also my torrent upload limit is set to be unlimited. So, that is not what the problem is.

Any suggestions on how to increase the upload speed?

Thank you!