9. (1) In a suit to which this Act applies or in amending a decree under the provisions of section 8, the court shall, notwithstanding anything to the contrary in any law, decree or contract or in any agreement purporting to close part transactions, determine the principal and take into account all sums paid by or on behalf of the debtor and in the case of a mortgage with possession, the net profit realized by the mortgagee or which with the exercise of ordinary diligence might have been realized by him, and shall determine the amount, if any, due by the debtor in accordance with the provisions of the following sub-sections :
Provided that for the purpose of determining the principal, the court shall treat as principal any accumulated interest which has been converted into principal any statement or settlement of account or by any contract in the course of the transaction before the first day of January, 1917, but shall treat as interest any accumulated interest which has been converted as aforesaid at any such statement, settlement or contract made on or after that date.
(2) The amount due by the debtor shall not exceed the amount that would have been due if the rate of interest had been, in the case of a secured loan, four and a half percent, per annum simple interest, and in the case of an unsecured loan six per cent. per annum simple interest.
(3) The amount due by the debtor as interest shall not exceed the amount of the principal outstanding on the date on which the amount due by the debtor is determined.
(4) Nothing in this section shall entitle the debtor to a refund of any sum already paid by him.