Thats not quite right.

First, here is a result for algebras that is quite useful to know:

If is a set and is a -algebra on then

is closed under countable intersections.

Proof:

Let for Then note that for each we have that where is the complement of It follows that

But other than that I can point out that are not themselves sets and can not possibly be in the -algebra. However, I think you meant , which is correct.

You are however, missing some sets in this. Consider this corollary to the previous result: if then This means that for example along with a few other sets.