Create a two-variable addition calculator cal_sum(a, b) that returns the sum of the two variables.

好的，我可以回答这个问题。以下是代码：

#include <stdio.h>

int cal_sum(int a, int b) {
    return a + b;
}

int main() {
    int a = 5;
    int b = 7;
    int sum = cal_sum(a, b);
    printf("The sum of %d and %d is %d\n", a, b, sum);
    return ;
}

输出结果为：The sum of 5 and 7 is 12。