Using the rules of inferences I know the rules of inferences and logical equivalence but I cannot seem to validate this argument.  I rewrote the first premise as $\neg p\vee q$ other from that I am stuck.  Any help will be appreciated. 

$$
\begin{array}{c}
p \to q \\
(q \land r) \to s \\
r \\
p \\ \hline
s
\end{array}
$$
Since $p$ and $p\to q$, we have $q$ by modus ponens.
Since $q$ and $r$, we have $q \land r$ by definition of conjunction.
Since $q \land r$ and $(q \land r) \to s$, we have $s$ by modus ponens.