The Oklahoma Department of Aerospace and Aeronautics is hereby authorized and empowered to offer for sale, sell and execute oil and gas leases, and other mineral and mining leases, and agricultural leases on any of the lands of this state under the control and supervision of the Department, provided, the development of land for the purpose leased will not unduly interfere with the aeronautical purpose for which said land is being used by the state. The Department is hereby given authority to adopt and promulgate such additional rules and regulations, not inconsistent herewith, as it may deem necessary and for the best interest of the state in facilitating the sale of said leases. It shall be the duty of the Director of the Oklahoma Department of Aerospace and Aeronautics to execute such leases for and in behalf of the Department, and the Director shall be liable on his official bond for failure to faithfully discharge his duties hereunder. The sales of all oil, gas and mineral leases shall be made upon the basis of a retained royalty of not less than one-eighth (1/8) of all oil, gas, casinghead gas, and other minerals produced from the lands covered by such leases and such additional cash bonus as may be procured. Provided, however, if the state owns less than one hundred percent (100%) of the oil, gas, casinghead gas and other minerals covered by any such lease, the royalty retained shall not be less than one-eighth (1/8) of the mineral interest so owned. All oil, gas, mineral and agricultural leases shall be sold only after advertisement for a period of three (3) weeks in a legal newspaper published and of general circulation in the county in which said lands are located. The sale shall be made to the highest and best bidder and all bids shall be in sealed envelopes and opened and considered at the same time.