question: 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?
#1 return the  Egyptians  withdrew from  the     Yemeni seaboard 
#2 return the  Egyptians  did obtain a firman from  the     Ottomans which secured their claims over the   city 
#3 return year of #1 
#4 return year of #2 
#5 return difference of #3 and  #4