Hello, I apologize if this is the wrong section to post this in.

There is an exercise Category Theory by Awodey that asks whether some categories are isomorphic. One is the category of sets and its opposite. I figured it wouldn't be since a function need not have an inverse. Although, I kept thinking such a functor preserved objects, but then, there are probably functors that don't do that and so maybe something else could work. But a quick google showed that these are not isomorphic, but I don't know where to begin to show that....

I thought maybe there's a result but the book hasn't gotten very far with anything so I'm guessing this should be straight forward?

I'm sorry, I'm totally new to category theory :S