Change dt and then click Run Again. dt =

tmax=10; if (firsttime) { InitGraph(); ScaleWindow(0,0,tmax,40); DrawAxes(); } Label('dt = '+dt,5,20*Math.random()); var k = .5; var phi = Math.exp(-k * dt); //Coefficients var gamma= (1 - phi) / k; // for an exact solution x=0; //Initial level 0 to 40 u=15; //Input flow 0 to 20 Colour(Black); var t=0; LineStart(t,x); while (t<tmax) { x = phi*x + gamma*u; //This is the simulation t = t + dt; LineTo(t, x); //This displays the result }