Problem $3$: Use formal deduction rules to prove the following. You can use the theorems on slide $61$ of the Week $4$ notes without proving them. $($a$)\{($p $$ q$)$ r$,$ s $$p$,$ t$,$s $$ t $$ q$\}$ r$.[7$ marks$]($b$)($s $$ p$)($t $$ q$)($s $$ q$)($t $$ p$).[6$ marks$]($c$)\{($p $($q $$ r$),$q$,$r$\}$p$.[5$ marks$]($d$)\{$c $$ n $$ t$,$ h $$s$,$ h $($s $$ c$)$ p$\}($n $$t$)$ p$.$