Select all the reasons that explain why f(x) is discontinuous at x = a.
1) f(x) is not defined at x = a.
2) f(x) is defined and exists, but f(a) is not defined.
3) f(x) is defined and exists, but f(a) is not equal to f(x).
4) f(x) and f(a) both exist, but they are not equal.
5) None of the above.
