(2) The extent to which the assets of the company are to be deemed to be included as aforesaid shall be the proportion ascertained by comparing the aggregate amount of the benefits accruing to the deceased from the company in the last three accounting years with the aggregate amount of the net income of the company for the said years: Provided that--
(a) where, in any of the said accounting years, the company sustained a loss, the amount of that loss shall be deducted in ascertaining the said aggregate net income of the company;
(b) where the company came into existence in the last year but one, or in the last, of the said accounting years, the references in this sub- section to the said accounting years shall be construed as references to the last two, or, as the case may be, the last, of those years.