Почуствуй разницу

Код:
a = function () {
trace ("a: cx=" + cx);
cx = 5;
trace ("a: cx=" + cx);
};
cx = 4;
a ();
trace ("_root: cx=" + cx);
trace ("---------------------");
b = function () {
trace ("b: dx=" + dx);
var dx = 15;
trace ("b: dx=" + dx);
};
dx = 14;
b ();
trace ("_root: dx=" + dx);