Efficiency of p in binom(n,p)

Hi. I have this problem.

Let $\displaystyle Y~binom(n,p)$ and set $\displaystyle \hat{p}=\frac{Y}{n}$.You may assume that $\displaystyle E(\hat{p})=p$ and $\displaystyle Var(\hat{p})=\frac{p(1-p)}{n}$.

a) What is the efficiency of $\displaystyle \hat{p}$ as an estimator of $\displaystyle p$?

b) Find the Rao-Cramer lower bound for the variance of unbiased estimators of p.

I think i'm okay with part b)

but part a) is what bugging me. What is the efficiency of a binomial of p?