what do we mean by internal rate of return, net present value and average annual return on investments? What do they imply? And, how are they computed?

This sounds like a homework question. If so, we are not here just to answer it for you. You need to make some attempt to answer them yourself first and show us you've made that attempt. i.e. What do you think the answers are? If you will post that, then someone can go over it, let you know if you're on the right track, etc.

I would also suggest either posting this in the homework help section, or at least under finance since that's what it is.