Instructions: Enter the harvesting function in the text box. You
may enter either a function of p (e.g. .05*p) or a constant (e.g. 100).
After entering the harvesting function, press the Enter key to
draw the graph of population vs. time with this harvesting function. The
most recent graph will be drawn in yellow while previous graphs will
appear in green. When the window becomes too crowded with graphs, press
the Clear Graph button to erase all but the most recent graph.