$3\mathrm{.}1$ Write out the equation for trigram probability estimation $($modifying Eq$.3\mathrm{.}11).$ Now write out all the non$-$zero trigram probabilities for the I am Sam corpus.

$P(w_n|w_{n-1})=\frac{C(w_{n-1}{w}_n)}{C(w_{n-1})}$