Consider a vocabulary with only four propositions, A$,$ B$,$ C$,$ and D$.$ How many models are there for the following sentences?

a$.BvvC.$

b$.$ notAvvnotBvvnotCvvnotD.

c$.)=>(B.$

d$.(A^{{?}^{?}}B)vv(C^{{?}^{?}}D).$

e$.B=>(A^{{?}^{?}}B).$