(a) Explain what is the syntax and semantics of propositional logic. (b) Explain what is a formal proof system. In your own words, explain the mean- ing of the concepts of soundness and completeness. [4 marks] (c) Show the logical equivalence of p -> q - _ and p/q - 1. (f) Show that = p V -p and p V -p. For the second part, you can assume (e), i.e. you can treat -(p V -p) -+ pA -p as an assumption. [4 marks]