How many months after the US recognized the independence of Armenia did it then open an embassy in the capital city of Armenia, Yerevan?
return the  US recognized the   independence of Armenia ;return the  US open an embassy in  the   capital city of Armenia ,  Yerevan ;return month of #1 ;return month of #2 ;return the  difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']