For the following two questions, we consider this program (the included headers are removed to save space). int x = ?; void* add (void *arg) { * += 20; printf("%d\\", x); //A int main( ) { pthread_t t; * += 20; pthread_create (&t, NULL, add, NULL); pthread_join(t, NULL); x -= 20; printf ("%d'\\", x) ; //B The initial value of x will be provided in the following questions