How many yards longer was Nedney's average length of field goals than Rackers' average length of field goals?
return Nedney ;return field goals of #1 ;return yards of #2 ;return average of #3 ;return Rackers ;return field goals of #5 ;return yards of #6 ;return average of #7 ;return difference of #4 and  #8
['select', 'project', 'project', 'aggregate', 'select', 'project', 'project', 'aggregate', 'arithmetic']