//  Scott DeRuiter   7/1/2002
//  Balloon.java
//  A Balloon that rises and falls, to be used by clients

public class Balloon   
{

	double altitude;
	double elapsedtime;
	double oldaltitude;
	double oldelapsedtime;

	public Balloon ( )   
	{
		altitude = 0.0;
		elapsedtime = 0.0;
		oldaltitude = 0.0;
		oldelapsedtime = 0.0;
	}

	public void ChangeAlt ( double change, double newtime )   
	{
		oldaltitude = altitude;
		oldelapsedtime = elapsedtime;
		altitude += change;
		elapsedtime += newtime;
	}

	public double Rate ( )   
	{
		return ( ( altitude - oldaltitude ) / ( elapsedtime - oldelapsedtime ) );
	}
	
	public double SendTime ( )   
	{
		return elapsedtime;
	}

	public double SendAlt ( )   
	{
		return altitude;
	}
}

//  Scott DeRuiter     7/1/2002
//  BalloonFlight.java
//  Simulates the flight of a balloon using the Balloon class.
//  7/15/2011 - Greenstein: Changed TextReader to Scanner

import java.util.Scanner;

public class BalloonFlight   
{
	public static void main ( String [] args )   
	{
		
		double alt, time;
		Scanner input = new Scanner ( System.in );

		Balloon myballoon = new Balloon ( );
		System.out.println ( "Altitude =  " + myballoon.SendAlt ( ) );
		System.out.println ( "Time     =  " + myballoon.SendTime ( ) );

		System.out.print ( "\n\nEnter the change in altitude  ->  " );
		alt = input.nextDouble ( );
		System.out.print ( "\nEnter the change in time      ->  " );
		time = input.nextDouble ( );

		myballoon.ChangeAlt ( alt, time );
		double rate = myballoon.Rate ( );

		System.out.println ( "Altitude =        " + myballoon.SendAlt ( ) );
		System.out.println ( "Time     =        " + myballoon.SendTime ( ) );
		System.out.println ( "Rate of Ascent =  " + myballoon.Rate ( ) );

		System.out.print ( "\n\nEnter the change in altitude  ->  " );
		alt = input.nextDouble ( );
		System.out.print ( "\nEnter the change in time      ->  " );
		time = input.nextDouble ( );

		myballoon.ChangeAlt ( alt, time );
		rate = myballoon.Rate ( );

		System.out.println ( "Altitude =        " + myballoon.SendAlt ( ) );
		System.out.println ( "Time     =        " + myballoon.SendTime ( ) );
		System.out.println ( "Rate of Ascent =  " + myballoon.Rate ( ) );
	}
}