How many more points did Mark Aguirre average per game compared to Derek Harper?
return Mark Aguirre ;return Derek Harper ;return points per game of #1 ;return points per game of #2 ;return the  average of #3 ;return the  average of #4 ;return the  difference of #5 and  #6
['select', 'select', 'project', 'project', 'aggregate', 'aggregate', 'arithmetic']