程序代码：

程序如下:
建立一个二维数组，存储星期一到星期五每天早、中、晚三个时段的温度。
然后输出星期一到星期五每天的平均温度。
但是我每次都得不出正确答案。
到底是哪里出错了，请大家指正一下！！！


#include <iostream>
#include <string>
using std::cout;
using std::cin;
using std::string;
using std::endl;
int main(){
    int a,b,sum=0;
    float aver=0;
     float air_humidity[4][2];
    for(a=0;a<5;a++)
    {
    switch(a){       
    case 0:cout<<"enter the monday is: "; break;
    case 1:cout<<"enter the Tuesday is: ";break;
    case 2:cout<<"enter the wednesday is: ";break;
    case 3:cout<<"enter the thursday is: ";break;
    case 4:cout<<"enter the friday is: ";break;
         }             
    for(b=0;b<3;b++)
     {if(b==0)  cout<<"please enter morning: ";
          else if(b==1)  cout<<"please enter afternoon: ";
          else cout<<"please enter night: ";
         cin>>air_humidity[a][b]; }
    }
   for(a=0;a<5;a++)
   {
   switch(a){       
    case 0:cout<<"the monday is: "; break;
    case 1:cout<<"the Tuesday is: ";break;
    case 2:cout<<"the wednesday is: ";break;
    case 3:cout<<"the thursday is: ";break;
    case 4:cout<<"the friday is: ";break;
         }             
   for(b=0;b<3;b++)
   { sum=sum+air_humidity[a][b];}
    aver=sum/3;
     cout<<aver<<endl;
     sum=0;
   }
  system("pause");
}