How many years after Simpson began resurveying trails from Fort Leavenworth to Utah did Wells Fargo & Co. haul mail, freight, and passengers along his route?
return Simpson began resurveying trails from  Fort Leavenworth to Utah ;return Wells Fargo & Co. did haul mail ,  freight ,   and  passengers along his route ;return year of #1 ;return year of #2 ;return difference of #3 and  #4
['select', 'select', 'project', 'project', 'arithmetic']