If any of the bonds for which the sinking fund was established are not yet due but are then redeemable under optional provisions, the money in the sinking fund is not subject to investment but shall be used and applied in payment and redemption of the bonds.
Limitation On Investment Of Sinking Funds
Mont. Code Ann. § 7-7-124, under General Provisions Related to Local Governments.
Mont. Code Ann. § 7-7-124