How many years after the 80-yard long roof was added to the United Road stand were roofs added to the south corners?
return the  80-yard long roof was  added to the   United Road stand ;return roofs were added to the  south corners ;return year of #1 ;return year of #2 ;return difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']