Apply the m.g.f. of the gamma distribution to find its expectation and variance.
Read post #2 here: http://www.mathhelpforum.com/math-he...ment-help.html
You should know this. If you need more help, please show all your work and say where you're stuck.
In fact, after recalling this thread http://www.mathhelpforum.com/math-he...stion-2-a.html
you should definitely know this. You're expected to learn something from the replies you get (if you're not simply trying to get answers for an assignment and don't care whether or not you understand anything).