Correct me if I'm wrong. I think we are forgetting that the question is not asking for the smallest integer.
the smallest value of y would be 5 x 3 x 2^2 in order for 450y = n^3 to be true
but, y could also be 5^4 x 3^4 x 2^5 and that would still make choices I, II and II into integers
Hope that's correct.
Must implies that "at any case or worst case scenerios". Those (y's value other than 2^2*3*5) are not the worst case scenerios.
Aaccording to the question: y must be at least 60 (or 2^2*3*5). if y is none othe r than 60, II and III cannot be an integer.
So none other B is an OA. Hope everybody agrees.