填空题 使用VC6打开考生文件夹下的工程test40_1，此工程包含一个源程序文件test40_1.cpp，但该程序运行有问题，请改正函数中的错误，使该程序的输出结果为：
The first result is 5
The second result is 2
The third result is 2
The fourth result is 6
源程序文件test40_1.cpp清单如下：
#include ＜iostream.h＞
int subtraction (int a, int b)

int r;
r=a-b;
/***************** found ************************/
return &r;

int main ()

int x=5, y=3, z;
z = subtraction (7,2);
cout ＜＜ "The first result is "＜＜ z ＜＜ '/n';
cout ＜＜ "The second result is "＜＜ subtraction(7,subtraction (7,2)) ＜＜ '/n';
/**************** found *************************/
cout ＜＜ "The third result is "＜＜ subtraction (&x,&y) ＜＜ '/n';
/***************** found ************************/
z= 4 + *subtraction (x,y);
cout ＜＜ "The fourth result is "＜＜ z ＜＜ '/n';
return 0;