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