第9题

#include <iostream>using namespace std;class Product {public:   Product(int n,int q,float p):num(n),quantity(q),price(p){};   void total();   static float average();   static void display();  private:   int num;   int quantity;   float price;   static float discount;   static float sum;   static int n; };void Product::total() {float rate=1.0;  if(quantity>10) rate=0.98*rate;  sum=sum+quantity*price*rate*(1-discount);  n=n+quantity; }void Product::display() {cout<<sum<<endl;  cout<<average()<<endl; }float Product::average() {return(sum/n);}float Product::discount=0.05;float Product::sum=0;int Product::n=0;int main() {   Product Prod[3]={     Product(101,5,23.5),Product(102,12,24.56),Product(103,100,21.5)    };   for(int i=0;i<3;i++)     Prod[i].total();   Product::display();   return 0; }