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