Write each sentence in symbolic form. Use p, q, r and s as defined below.

p ∶ Paul is a table tennis player.
q ∶ Paul is a basketball player.
r ∶ Paul is a rock star.
s ∶ Paul is a mechanical engineer.

(a) If it is not true that Paul is a table tennis player or a rock star, then Paul is a mechanical engineer.
(b) Paul is a basketball player, if and only if he is not a football player and he is not a rock star.
(c) If Paul is a mechanical engineer, then he is a basketball player and he is not a table tennis player.