In addition to any capital expenditure surcharge permitted by section 4-5-304 of this article, the landlord may pass through to the tenant of an apartment unit the cost of any improvement mandated by any government statute, rule, or regulation enacted after March 24, 1981, including interest or the value of capital up to eighteen percent (18%) per annum, allocated among all the dwelling units of the building in proportion to their size, determined in square feet, and annualized in accordance with the straight line depreciation schedules allowed under the federal income tax laws. (1962 Code § 11-3.05; amd. 1988 Code)