6.—(1) Where the amount of monthly instalment which a member is required to pay to a lender under a mortgage loan of a house or flat, or to the Housing and Development Board or a Town Council in respect of improvement contributions for upgrading works or lift upgrading works (as the case may be), is increased or reduced because of a change —
(a)
in the rate of interest on the mortgage loan or in the quantum of the mortgage loan disbursed in relation to the house or flat; or
(b)
in the rate of interest on the improvement contribution or in the quantum of the improvement contribution payable,
the Board is entitled to make the necessary adjustment when computing the amount of monthly instalment payable by the member.
(2) Where a house or flat is jointly owned by 2 or more persons, the Board will, if none of the joint owners by notice in writing to the Board indicates otherwise, require the monthly instalment payable —
(a)
by the joint owners under a mortgage loan of the house or flat to be in the same proportion as that before the change in the rate of interest on the mortgage loan or in the quantum of the mortgage loan disbursed; or
(b)
by the joint owners in respect of improvement contributions in relation to the house or flat to be in the same proportion as that before the change in the rate of interest on the improvement contribution or in the quantum of the improvement contribution payable.