(1) Every savings bank shall regulate the rate of interest upon the amounts to the credit of depositors therewith, in such manner that depositors shall receive as nearly as may be all the earnings of the bank after transferring the amount required by RCW
32.08.120 and such further amounts as its trustees may deem it expedient and for the security of the depositors to transfer to the guaranty fund, which to the amount of ten percent of the amount due its depositors the trustees shall gradually accumulate and hold. Such trustees may also deduct from its net earnings, and carry as reserves for losses, or other contingencies, or as undivided profits, such additional sums as they may deem wise.
(2) Every savings bank may classify its depositors according to the local market, character, amount, regularity, or duration of their dealings with the savings bank, and may regulate the interest in such manner that each depositor shall receive the same ratable portion of interest as all others of his or her class.
(3) Unimpaired contributions to the initial guaranty fund and to the expense fund, made by the incorporators or trustees of a savings bank, shall be entitled to have dividends apportioned thereon, which may be credited and paid to such incorporators or trustees.
Whenever the guaranty fund of any savings bank is sufficiently large to permit the return of such contributions, the contributors may receive interest thereon not theretofore credited or paid at the same rate paid to depositors.
(4) A savings bank may pay interest on deposits at such rates as its board or a committee or officer designated by the board shall from time to time determine.
(5) The trustees of any savings banks, other than a stock savings bank, whose undivided profits and guaranty fund, determined in the manner prescribed in RCW
32.12.070, amount to more than twenty-five percent of the amount due its depositors, shall at least once in three years divide equitably the accumulation beyond such twenty-five percent as an extra dividend to depositors in excess of the regular dividend authorized.
(6) A notice posted conspicuously in a savings bank of a change in the rate of interest shall be equivalent to a personal notice.