listPairs = [(a*b, y) | a <- [0..], b <- [0..], (a*b) > 5, (a*b) < 500,

(y*y) < 1001, mod y x == 0]

Now I have it as you said, however the compiler complains about all y and x
and says they are NOT in scope.

Why is it so? I can't see any problem with that...