The real estate bond funds on deposit with the state treasurer must be maintained in the sums needed to pay outstanding valid enforceable real estate series bonds of the state of North Dakota and lawful interest thereon. All money in said funds not needed for such bonds and interest must upon the effective date of sections 54-30-29 through 54-30-33 be transferred by the state treasurer to the general fund in accordance with the provisions of subsection 2 of section 54-30-11.