text: #include <iostream>
  #include <string>
  
  #include "Sa.h" 
  using namespace std;
  
  int main(int argc, char **argv)
  {
      Sales_data data1, data2;
  
      double price = 0;
  
      cin >> data1.bookNo >> data1.units_sold >> price;
      data1.revenue = data1.units_sold * price;
      
      cin >> data2.bookNo >> data2,units_sold >> price;
      data2.revenue = data2.units_sold * price;
  
      if(data1.bookNo == data2.bookNo)
      {
          usigned totalCnt = data1.units_sold + data2.units_sold;
          double totalRevenue = data1.revenue + data2.revenue;
          
          cout << data1.bookNo << " " << totalCnt << " " 
               << totalRevenue << "  ";
  
          if(totalCnt != 0)
              cout << totalRevenue/totalCnt << endl;
      }
      else
      {
          cerr << "Data must refer to hte same ISBN" << endl;
          return -1;
      }
  
  
      return 0;
  }
  