Basic sets

I'm having problems with questions g) and k).

For g), apparantly the answer is i) but it seems to me they're all the same.If |b'| is a finite subset of an infinite set, then |b| must be an infinite set as N is infinite. Is there any difference between saying "b is infinite" and "|b| = infinity"?

For k), apparantly the answer is i) as well, but I still don't understand the notation. Could someone explain it through?.

Page in question: http://i38.tinypic.com/142ev41.jpg

>>40

Hey, you're speaking to the converted, note the past tense.

Copy and paste was used A LOT.

>>41
Please tell me you did NOT use only 3 letter variable names...

>>42

Of course not. I called them i,j,k  etc for integers
and x,y,z for doubles.

OBVIOUSLY.

Ps. I do of course fail at programming.