Applet Code
Supply Function with Varying Cost

import java.awt.*;
import java.applet.*;
import java.lang.*;

public class SupplyCostC extends Applet
{
       Panel             tpanel = new Panel();
       private TextField tfield = new TextField("0.40");

       String            ttext  = "0.40";

       double            t      = 0.4;

       Graphics          sG;
       Graphics          bG;
       Image             bI;

       Color             black        = new Color(0, 0, 0);
       Color             white        = new Color(255, 255, 255);
       Color             back         = new Color(247, 243, 234);
       Color             grid         = new Color(64, 255, 64);
       Color             red          = new Color(255, 64, 64);
       Color             blue         = new Color(96, 96, 255);
       Color             gray         = new Color(64, 64, 64);

       int               width        = 440;
       int               wholewidth   = 441;
       int               height       = 200;
       int               wholeheight  = 201;
       int               top          =  40;
       int               margin       =  20;

       int               px, py;

       public void init()
       {
              bI = createImage(wholewidth, wholeheight + 2 * margin);
              bG = bI.getGraphics();
              drawback();

              setBackground(back);
              setFont(new Font("Courier", Font.BOLD, 12));
              tpanel.setBackground(back);
              tpanel.setFont(new Font("Courier", Font.BOLD, 12));
              tpanel.add(new Label(" c: "));
              tpanel.add(tfield);
              tpanel.add(new Button("Move"));
              add(tpanel);
       }

       public void paint(Graphics g)
       {
              g.drawImage(bI, 0, top, this);
              sG = getGraphics();
       }

       public void update(Graphics g)
       {
              g.drawImage(bI, 0, top, this);
       }
 
       public void drawback()
       {
              bG.setColor(back);
              bG.fillRect(0, 0, wholewidth, wholeheight + top);
              bG.setColor(black);
              bG.drawLine(xscale(0.0), yscale(0.0), xscale(5.0), yscale(0.0));
              bG.drawLine(xscale(0.0), yscale(0.0), xscale(0.0), yscale(5000.0));
              for (int i = 0; i < 11; i = i + 1)
              {
                  bG.drawLine(xscale(0.0) - 2, yscale(0.0 + i * 500.0),
                              xscale(0.0) + 2, yscale(0.0 + i * 500.0));
                  bG.drawLine(xscale(0.0 + i * 0.50), yscale(0.0) - 2,
                              xscale(0.0 + i * 0.50), yscale(0.0) + 2);
              }
              bG.drawLine(xscale(t), yscale(0.0), xscale(5.0),
                          yscale(1000.0 * (5.0 - t)));              
       }

       public int xscale(double x)
       {
              int ix;
              ix = (int) Math.round(margin + 80.0 * x);
              return ix;
       }
 
       public int yscale(double y)
       {
              int iy;
              iy = (int) Math.round(margin + height * (1 - y/5000));
              return iy;
       }

       public boolean mouseDown(Event evt, int mx, int my)
       {
              if ((my > top + margin + height - 5) &&
                  (my < top + margin + height + 5))
              {
                  t = (mx - margin)/80.0;
                  tfield.setText(java.lang.Double.toString(t));
              }
              else
              {
                  ttext = tfield.getText().trim();
                  t = Double.valueOf(ttext).doubleValue();
              }
              drawback();
              sG.drawImage(bI, 0, top, this);
              return true;
       }

       public boolean action(Event evt, Object arg)
       {
              if (arg.equals("Move"))
              {
                  ttext = tfield.getText().trim();
                  t = Double.valueOf(ttext).doubleValue();
                  drawback();
                  sG.drawImage(bI, 0, top, this);
              }
              return true;
       }
       
}