You need APLIA.
Its your HW.
Buy the textbook/aplia package from UCI, because to purchase aplia by itself costs the same as the bundle that they sell at UCI.
In other words, if you're buying the textbook used from someone else, chances are that APLIA will not be included. And now you're stuck with purchasing APLIA from the actual site, which is the same price as the textbook/APLIA bundle at UCI bookstore.