How many  yards longer was Robbie Gould's longest field goal than Ryan Longwell's longest field goal?
return Robbie Gould ;return Ryan Longwell ;return field goals of #1 ;return field goals of #2 ;return yards of #3 ;return yards of #4 ;return the  longest of #5 ;return the  longest of #6 ;return the  difference of #7 and  #8
['select', 'select', 'project', 'project', 'project', 'project', 'aggregate', 'aggregate', 'arithmetic']