Please solve step by step

Question $1(10\%)$ Let $A,B,$ and $C$ be propositional wffs$.$ Write a wff whose meaning

is $"$if A then $B$ else $C".$

Question $2(15\%)$ Use truth table to verify following equivalences.

$($a$)PQ-=$notPvvQ

$($b$)$ not$(P^{{?}^{?}}Q)-=$notPvvnotQ

$($c$)$ Avv$(A^{{?}^{?}}B)-=A$

Question $3(10\%))$ Show that $$ is not associative. That is$,(AB)CA$

$(BC).$

Question $4(15\%)$ Use Quine's method to show each wff below is a contingency.

$($a$)(AB{)}^{{?}^{?}}(B$notA$)A$

$($b$)(AB{)}^{{?}^{?}}(BC)(CA)$

$($c$)(AvvB)(CvvA{)}^{{?}^{?}}(notCvvB)$