Exercise 7.9

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

1. $B\lor C$.

2. $\lnot A\lor \lnot B \lor \lnot C \lor \lnot D$.

3. $(A{:\;{\Rightarrow}:\;}B) \land A \land \lnot B \land C \land D$.

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