82. Every contribution bears interest, from the first day of the month that follows the month during which it should have been paid into the pension fund or to the insurer, at the rate of return derived from the investment of the plan assets, less investment expenses and administration costs, or, if the plan so provides and to the extent that the contribution relates to refunds or pension benefits that remain insured, at the monthly rate of return on personal 5-year term deposits with chartered banks, as compiled by the Bank of Canada.