Working on some homework problems, and kind of stuck. I thought I had a handle on this, but not so much.

Here is the problem:

What I did is take the anti derivative, which is t^5/5.. then plug in the values and subtract. So I get 20^5/5 - x^5/5 to be the answer.. but thats wrong. I don't know if I'm missing a step or doing something wrong. Any help would be greatly appreciated.

Thanks!