Consider the following C program, list all visible variables for each of the 4 marked points throughout the program. You may want to use the number of the definition statement that defines it, e.g, a1, b1, c1 in definition 1; b2, . in definition 2, etc.

void fun(void) { int a, b, c; /* definition 1 */ while (. . .) { int b, c, d; /* definition 2 */ . . . < Point 1 while (. . .) { int c, d, e; /* definition 3 */ . . . < Point 2 } . . . < Point 3 } . . . < Point 4 }