How many years after the Egyptians withdrew from the Yemeni seaboard did the Egyptians obtain a firman from the Ottomans which secured their claims over the city?
return the  Egyptians  withdrew from  the     Yemeni seaboard ;return the  Egyptians  did obtain a firman from  the     Ottomans which secured their claims over the   city ;return year of #1 ;return year of #2 ;return difference of #3 and  #4
['select', 'select', 'project', 'project', 'arithmetic']