5.6

#define  _CRT_SECURE_NO_WARNINGS
#include<iostream>
using namespace std;
int main()
{
const int Years = 3;
const int Months = 12;
const char* Month[Months] =
{
"January",
"February",
"Match",
"April",
"May",
"June",
"July",
"August",
"September",
"October",
"November",
"December"
};
int sales_volume[Years][Months];
int sum[3] = {0,0,0};
for (int k = 0; k< Years; k++)
{
cout << "In the " << k + 1 << " year,the out sales volume of books is :" << endl;
for (int i = 0; i < Months; i++)
{
cout << "Enter the sales volume in " << Month[i] << ':';
cin >> sales_volume[k][i];
sum[k] += sales_volume[k][i];
}
cout << "This year out whole sales volume is " << sum[k] << endl;
}

cout << "And the 3 years we sold " << sum[0] + sum[1] + sum[2] << " altogether!" << endl;
return 0;
}