unbiased estimators

I having some issues with a stat problem. I would appreciate any help
that I could get.

Here it is:

Suppose Y1,...,Yn denote a random sample of size n from a Gamma
distribution with parameters ALPHA and BETA=5. Let

AlphaHat1 = YBar/5

&

AlphaHat2 = (2Y1 - Y2 + 4Y3)/25


a Show that AlphaHat1 and AlphaHat2 are both unbiased estimators of
ALPHA

b Find V(AlphaHat1)

c Find V(AlphaHat2)

d For what values of n is AlphaHat1 a better estimator of AlphaHat2?
Why?

Thanks,

Jason

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