Construction.
315. In this Code, unless otherwise stated,—
(a) a reference to any income, or to the result of any computation, shall be construed as a reference to both the negative and positive variation of the income or the result, as the case may be;
(b) any direction for aggregation of two or more items, which are expressed as amounts, shall be construed also to include a direction for aggregation of negative and postive amounts in all their combinations;
(c) the value of any variable in a formula shall be deemed to be nil, if the value of such variable is indeterminable or unascertainable.
