9. Consider the following Python program: x = 1; y = 3; z = 5; def sub1(): a = 7; y = 9; z = 11; . . . def sub2(): global x; a = 13; x = 15; w = 17; . . . def sub3(): nonlocal a; a = 19; b = 21; z = 23; . . . . . . List all the variables, along with the program units where they are declared, that are visible in the bodies of sub1, sub2, and sub3, assuming static scoping is used.