Please provide explanation

Prove explanation add.c: #include "helper.h" int count; int res; int main () {add (4, 6); count++; printf ("%d and %d ", count, res); return 0;} helper.h: #ifndef __helper_h__ #define __helper_h__ #include extern int count; extern int res; void add (int a, int b) {count++; res = a + b;} #endif The code above is compiled using "gcc add.c". Output of the above program would be: 0 and 0 Undefined behaviour 1 and 10 2 and 10 1 and 0