1. The function sum() in figure 2.25 is called for the first time by the main program. From the second time on, it is called by itself. (a) How many times is it called altogether, including the call from main()? (b) Draw a picture of the main program variables and the run-time stack just after the function is called for the third time. Do not draw the stack frame for main(). You should have three stack frames.(c) Draw a picture of the main program variables and the run time stack just before the return from the call of part (b). You should have three stack frames, but with different contents from part (b).

I understand that in part (a) the function is called 4 times (Please correct me if I'm incorrect). I have trouble with questions b and c.

All help is appreciated

Fig 2.25

FIGURE 2.25 A recursive function that returns the sum of the first n numbers in a #include int list[41; int sum(int all, int n) f s the sum of the elem ents of a between a to1 and a tn // Return if n0) f return a [o]; else eturn al [n]sum(a, n 1); // ra2 int main ) printf ("Enter four integers: " scanf ("tdkdkd &list [0], &list [1], &list [21, printf("Their sum s: %d ", sum (list, 3)); return 0; &list [21,&list [3]) &li Interactive Input/Output Enter four integers: 3 264 Their sum is: 1!5