3.11

#include <iostream>using namespace std;class Time;class Date{public:    Date(int,int,int);    friend Time;private:    int month;    int day;    int year;};Date::Date(int m,int d,int y):month(m),day(d),year(y){ }class Time{public:    Time(int,int,int);    void display(const Date &);private:    int hour;    int minute;    int sec;};Time::Time(int h,int m,int s):hour(h),minute(m),sec(s){ }void Time::display(const Date &d){    cout<<d.month<<"/"<<d.day<<"/"<<d.year<<endl;    cout<<hour<<":"<<minute<<":"<<sec<<endl;}int main(){    Time t1(10,13,56);    Date d1(12,25,2004);    t1.display(d1);    return 0;}