### How th work with enumerable and infinite set

Hello,

I am trying to do following: construct the set B that is the difference between QQ and the set of the prime numbers
(note that B is a countable set). Within Sage, I tried the following

```
X = Set(QQ)
Y = Set(Primes())
B = Set(X.difference(Y))
B.cardinality()
```

then I press evaluate. I am expecting that the cardinality of B is +Infinity. But Sage does not bring any result.

I tried this also initializing B like

```
B = InfiniteEnumeratedSets(RR).
```

Could anybody please give me a hint what I am doing wrong?

Thank you very much and regards.

vbk