// tanksale.java
// economic use of reserves
// adapted from a program in basic by H.T. Odum & E. Odum, 1994

import java.applet.Applet;
import java.awt.*;

public class tanksale extends Applet
{

 Label prompt1,prompt2;
 TextField input1,input2;
 double m,q;
 Button drawbutton;

 public void init()
 {
        prompt1 = new Label("M Total money supply: ");
        input1 = new TextField("1",7);
		add(prompt1);add(input1);

		prompt2 = new Label("           Q Storage: ");
		input2 = new TextField("1000",7);
		add(prompt2);add(input2);

		drawbutton = new Button("Draw");
		add(drawbutton);
 }

 public boolean action(Event e, Object o)
 {
        m=(float)Integer.parseInt(input1.getText());
		q=(float)Integer.parseInt(input2.getText());
		repaint();
		return true;
 }

 public void paint(Graphics g)
 {
        int t;
		double q0,m0,t0,dt,dm,dq;
		double i,p1,p2,k1,k2,k3,k4,k5,pr;
		dt=0.2;q0=0.13;m0=0.2;t0=10;i=1;p1=5;p2=1;
		k1=0.001;k2=0.000001;k3=0.0005;k4=1;k5=0.0003;t=0;
		g.drawRect(0,90,320,210);

		do
		{
		  g.setColor(Color.blue);
		  g.drawOval(t,(int)(300-q*q0),1,1);

			g.setColor(Color.red);
			if(300-m*m0>190)
			g.drawOval(t,(int)(300-m*m0),1,1);
			else
			g.drawOval(t,90,1,1);

			pr=q*(k4*m/p2);
			dq=k1*i-k2*q-k3*pr;
			dm=p1*k5*pr-k4*m;
			q=q+dq*dt;
			m=m+dm*dt;
			t=t+1;
		} while(t<=320);
	 }
	}
// Camila Duartem & E. Ortega, January 29th, 2001