The maximum number of compound propositions, out of $p \vee r \vee s, p \vee r \vee \sim s, p \vee \sim q \vee s$,
$ \sim p \vee \sim r \vee s, \sim p \vee \sim r \vee s, \sim p \vee q \vee \sim s, q \vee r \vee \sim s, q \vee \sim r \vee \sim s, \sim p \vee \sim q \vee \sim s $
that can be made simultaneously true by an assignment of the truth values to $p, q, r$ and $s$, is equal to