A biased six faced die has probability $p$ of showing a 3 when it is tossed. The random variable $X$ is the number of tosses up to and including third 3
(a) State the distribution of X
(b) Find $P(X = x)$, $x>3$
(c) Show that $Y = \frac{2}{(X-1)(X-2)}$ is an unbiased estimator of $p^2$
I've gotten the answers to (a) and (b), but I cannot solve (c). Anyone kind enough to provide a hint or the full length answer?