(a) The board of directors shall determine the rate and amount of interest to be paid on deposit accounts and, for that purpose, may establish reasonable classifications of accounts based on: types of classes of accounts; the length of time accounts are continued in effect; size of initial payments on accounts; minimum balances of accounts required for payment of interest; frequency and extent of the activity of accounts; or other classifications as the Commissioner may approve.
     (b) The board of directors shall determine by resolution the method of calculating the amount of any interest on deposit accounts and the date on which it is to be paid or credited.