The finance director of the City of Austin is hereby declared to be the ex-officio treasurer of said board. It is made the duty of the secretary, under the direction of said board, to collect, receive and pay into the city treasury, all moneys due on account of the operation of the utilities' facilities and proceeds from the sale of bonds, and to keep a set of books which shall contain a full and complete statement of the condition and operation of said works and plant of all moneys received and paid out by order of said board, and all debts due and owing said board for any cause whatever, together with an accurate account of all the expenses of said board; and the said secretary may appoint an assistant for whose acts he/she shall be responsible, who shall only be authorized to act in the absence or disability of said secretary; and in the case of the disability from absence or other cause of said secretary, the board may appoint a secretary pro-tem to perform the duties of such secretary. It is made the duty of the treasurer of said board to receive all moneys which may be paid into the treasury on account of said board from any source whatever, and all moneys so received shall be retained by said treasurer and credited to the account of the board, and paid out only upon the orders of said board signed by its president and secretary, except such money as may be received from the sale of bonds and frontage tax, which shall be credited to the general account of the city and paid out upon the order of the mayor and city treasurer, and shall keep a detailed and exact account thereof in such manner as to show at all times the exact financial condition of said board. The books of said board shall be open to the examination of any person or persons appointed for that purpose, or to any member or committee of the city council or other person interested in the affairs of said city.