How many months passed between Erard taking up position in Noyers and the Blanche of Navarre besieging it?
return Erard taking up position in  Noyers ;return the  Blanche of Navarre besieging Noyers ;return when  was  #1 ;return when  was  #2 ;return difference of #4 and  #3 in  months
['select', 'select', 'project', 'project', 'arithmetic']