How many years passed between the region being annexed by the Kingdom of Prusia and it becoming part of the German Empire?
return the  region being annexed by the   Kingdom of Prusia ;return the  region becoming part of the   German Empire ;return year of #1 ;return year of #2 ;return the  difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']