How many years passed between the First Crusade and the fall of the Vounty of Edessa?
return the  First Crusade ;return the  fall of the   Vounty of  Edessa ;return when  was  #1 ;return when  was  #2 ;return difference of #4 and  #3 in  years
['select', 'select', 'project', 'project', 'arithmetic']