I will ask you to prove that something is or is not injective and/or surjective and/or bijective. This is of the style of Section 12.2. So read 12.2 and do exercises for Section 12.2 to prepare. It will be very similar, if not identical, to one of these or to examples 12.4 or 12.5. The methods are shown on pages 202 and 203.