Not later than seventy-five days before the end of each fiscal year the Library Board shall furnish the City Council with an estimate of the annual budget required for the ensuing fiscal year, which budget shall be submitted to the Council for approval or rejection at the time the general budget of the City is so submitted. If rejected the Council may either amend the budget and approve the same as amended, or may return said budget to the Library Board with reasons for its rejection, and request said amended budget from said Board. When the library budget has been approved by the Council, the Council shall levy such tax as may be necessary to meet the budget appropriation for library purposes. The Library Board shall not expend in any one year a greater amount than the amount so approved by the Council when fixing the budget appropriation for library purposes. However, the Council may by resolution authorize additional expenditures by the Library Board and appropriate money therefor.(1981 Code § 1.136)