The plot request plots Expenditures on the vertical axis, plots DropoutRate
on the horizontal axis, and specifies an asterisk as the plotting symbol.
HREF= draws a reference line extending from 28.6 on the horizontal axis. The
reference line represents the national average.
plot expenditures*dropoutrate='*' / href=28.6;
title 'Plot of Dropout Rate and Expenditure Per Pupil';