#include #include "stdio.h" #include class Date{ int ngay,thang,nam; friend class HD; }; class KHACH{ char mk[10],tk[30],phone[15]; public : void nhap(); void xuat(); }; class HANG{ char mh[10],th[40]; int solg; float dongia; public : void nhap(); void xuat(); friend class HD; }; class HD{ int k,sohd; Date ngaylap; KHACH y; HANG H[40]; float tongtien; public : void nhap(); void xuat(); }; void KHACH::nhap() { cout cout cout } void KHACH::xuat() { cout cout cout } void HANG::nhap() { cout cout cout>dongia; cout>solg; } void HANG::xuat() { cout cout cout cout } void HD::nhap() { cout>sohd; cout cin>>ngaylap.ngay>>ngaylap.thang>>ngaylap.nam; cout y.nhap(); cout>k; cout for(int i=0;i { cout H[i].nhap(); } float tg=0; for(int j=0;j tg=tg+H[j].dongia * H[j].solg; tongtien=tg; } void HD::xuat() { cout cout cout y.xuat(); cout for(int i=0;i { cout H[i].xuat(); } cout } void main() { HD X; cout X.nhap(); cout X.xuat(); getch(); }...