Whenever the National Guard Members’ Finance Committee finds that the interest rate then fixed and charged by the department on any purchase contract is not adequate to meet the covenants or requirements of any resolution of issuance, the National Guard Members’ Finance Committee shall specify the amount of the increased rate of interest to be charged on all purchase contracts acquired with the proceeds of or otherwise allocable to the revenue bonds issued pursuant to the resolution of issuance on all purchase contracts if they bear a uniform rate of interest. The department shall increase the interest rate on those purchase contracts which are specified by the National Guard Members’ Finance Committee. Such increased interest rate will take effect on the first day of the second calendar month next succeeding the date of such action and shall remain in effect until such time as the National Guard Members’ Finance Committee consents to the reduction thereof. The National Guard Members’ Finance Committee shall not consent to any reduction in the interest rate then fixed unless:
(a) The revenues in the preceding fiscal year produced by the interest rate or rates then in effect are in excess of all requirements of all resolutions of issuance under which revenue bonds are then outstanding, and
(b) The interest rate or rates so reduced will produce revenues for each subsequent fiscal year while any revenue bonds are outstanding in the aggregate amount required by all resolutions of issuance under which such revenue bonds are outstanding.