Expected Ruin Time via Martingale Method

A biased random walk on $\{0, 1, \ldots, 10\}$ with absorbing barriers at $0$ and $10$ moves $+1$ with probability $p = 0.6$ and $-1$ with probability $q = 0.4$. Starting from state $3$, use the martingale $M_n = X_n - \mu n$ (where $\mu = p - q$) and the optional stopping theorem to find the expected absorption time $E[\tau]$.