The budget message submitted by the mayor to the board of aldermen shall explain the budget, shall contain an outline of the proposed financial policies of the city for the budget year, and shall describe the important features of the budget plan. It shall set forth the reasons for salient changes from the previous year in cost and revenue items and shall explain any major changes in financial policy. It shall include a statement of pending capital projects of a capital program for the next five fiscal years. Attached to the budget message shall be such supporting schedules, exhibits and other explanatory material, in respect to both current operations and capital improvements, as the mayor shall believe useful to the board of aldermen. (Acts 1951, ch. 539, § 80)