1) if we have p = 0 q=0 we get :
=(p V q) <-->p' & ( !p <--->q') &a
=0 <---> p' &( !p <--->q') &a
=!(p' & (!P &(1<--->q') & a
=!p' & q' &a
2) if we have p=0 q= 1 we get :
=1 <----> p' & (!p<-->q') &a
=p' & (1<--->q') &a
=p' & q' &a
3) if we have p=1 q=0 we get :
=p' & (!p <--->q')&a
=p' & ( !p <---> q') &a
=p' & !q' & a
4) if we have p=1 q=1 we get :
=p'& (!p <---> q') &a
=p' & !q' & a