The affairs and business of any bank chartered after September 2, 1973, or which has had transfer of twenty-five percent or more of voting shares after September 2, 1973, shall be managed or controlled by a board of directors of not less than five and not more than fifteen members, who shall be selected from the stockholders at such time and in such manner as may be provided by the articles of incorporation of the corporation and in conformity with sections 8-101 to 8-1,121. Any bank chartered before September 2, 1973, may have a minimum of three directors and not more than fifteen directors so long as it does not have transfer of twenty-five percent or more voting shares, with such directors selected as provided in this section. Any vacancy on the board shall be filled within ninety days by appointment by the remaining directors, and any director so appointed shall serve until the next election of directors, except that if the vacancy created leaves a minimum of five directors, appointment shall be optional. The board shall select from among its number the president and secretary and shall select a cashier. Such officers shall hold their office at the pleasure of the board of directors. The board of directors shall hold at least one regular meeting in each calendar quarter, and at one of such meetings in each year a thorough examination of the books, records, funds, and securities held by the bank shall be made and recorded in detail upon its record book. In lieu of the one annual examination required, the board of directors may accept one annual audit by an accountant or accounting firm approved by the Director of Banking and Finance.