The department shall reimburse each designated area agency on aging for seventy-five percent of the actual cost of providing eligible activities and services as defined in section 81-2222. Such reimbursement shall be made from (1) state funds appropriated by the Legislature, (2) federal funds allocated to the department, including federal funds allocated under the Older Americans Act, as now or hereafter amended, and (3) other funds as available. The payments shall be made by the department on or before the twentieth day of each month. If state funds appropriated, federal funds allocated, or other funds available are insufficient to finance the department-approved plan and budget for each designated area agency on aging, the reimbursement to each area agency on aging shall be proportionately reduced. If an area agency on aging chooses to exceed the budget approved by the department, costs in excess of the approved budget shall not be reimbursed by the department.