sum0; scanf("%d", &x); while (x >= 0) { sumsum +X scanf ("%d", &x); Fig. 2.14. Summing a list of integers terminated by a negative integer. 2.5.4*: The fragment in Fig. 2.14 reads integers until it finds a negative integer, and then prints the accuiulated sum. What is an appropriate loop invariant for the point just before the loop test? Use the invariant to show that the fragment performs as intended