Differentiate between proposition and wff.

Show that the given statements are tautologies:

[(p ⇒ q) ^ (q ⇒ r)] ⇒ (p ⇒ r)

From premises A ⇒ B and B ⇒ A, conclude B' + A.B.

(i) Let P : He has fax and Q : He uses e-mail.
Write the following statement in terms of P and Q:
He has fax and he may or may not use e-mail.