using System;

class Abstraction {    //ABSTRACT CLASS

    protected Implementor imp;

public Implementor Implementor {

    set { imp = value ; }

}

public virtual void calculation() {

    imp.calculation();

}

}

​

abstract class Implementor {      //IMPLEMENTOR

public abstract void calculation();

}

​

class Refinedabstraction : Abstraction {

    public override void calculation() {

        imp.calculation();

    }}

​

class acclass : Implementor {          //CONCRETEIMPLEMENTOR1

    public override void calculation() {

    Console.WriteLine("FARE IS RS600 PER PERSON "); 

    }}

​

class nonacclass : Implementor {      //CONCRETEIMPLEMENTOR2

    public override void calculation() {

        Console.WriteLine("FARE IS RS300 PER PERSON "); 

    }}

​

public class main{

    public static void Main() {

        Abstraction ab = new Refinedabstraction();

        ab.Implementor = new acclass();

        ab.calculation();

        ab.Implementor = new nonacclass();

        ab.calculation();

    }}