(b) Construct truth-trees for following sequents and decide whether the following statement is true or not.
Is {!L, M & B} ⊨! Q! ? (Hint: you can read the question as asking: is Q the semantic consequence
of set {L! , M & B}?)
Is {!P → Q, ∼ Q} !⊨ ! ∼ P ? (Hint: you can read the question as asking: is! ∼ P the semantic
consequence of set {!P → Q, ∼ Q}?)
