According to the treaty, how many years after negotiation would the entire island of Ireland become a self-governing Dominion known as the Irish Free State?
return negotiations of the  treaty ;return the  entire island of Ireland would become a self-governing Dominion known as the   Irish Free State ;return year of #1 ;return year of #2 ;return the  difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']