use Arrays, functions, loop, and if-else

can someone help me how to start this Code, i don't understand exactly how to implement this code. i don't know how to start. I'm a beginner and this is a beginning class.

Code:Complete the following program. You will mainly implement three out of five functions used in this program! main() { /* Declare three integer arrays as follows */ int a[50], b[70], c[120]; /* Implement a function set_array_rand(int x[], int n) and call it to generate the values in array a and b randomly. */ set_array_rand(a, 50); set_array_rand(b, 70); /* Using the selection_sort(double x[], int n) function we implemented in class, sort the elements in a and b arrays. */ selection_sort(a, 50); selection_sort(b, 70); /* Implement a MERGE function and call it as follows to merge the values in arrays a and b into array c such that the values in c will be sorted after merging */ merge_sort(a, 50, b, 70, c, 120); /* Print the values in array c */ print_array(c, 120); } void set_array_rand(int x[], int n) { /* Randomly generate elements of x array */ for(int i=0; i< n; i++) x[i] = rand_int(30, 100); } int rand_int(int a,int b) { return rand()%(b-a+1) + a; } void selection_sort(int x[], int n) {/* YOUR CODE */} void merge_sort(int a[], int na, int b[], int nb, int c[], int nc) { /* merge the values in a and b into c while keeping the values sorted. For example, suppose we have the following arrays a = { 3, 7, 9, 12} and b = {4, 5, 10} When we merge these two arrays, we will get c = {3, 4, 5, 7, 9, 10, 12} *//* YOUR CODE */} void print_array(int x[], int n) {/* YOUR CODE */}