Whenever real property owned by the state of Washington and under the jurisdiction of the Washington state patrol is no longer required, it may be sold at fair market value, or otherwise disposed as permitted under RCW 39.33.015. Any such sale or disposal must be in accordance with RCW 43.17.400. All proceeds received from the sale of real property, less any real estate broker commissions up to four percent of the sale price, shall be deposited into the state patrol highway account: PROVIDED, That if accounts or funds other than the state patrol highway account have contributed to the purchase or improvement of the real property, the office of financial management shall determine the proportional equity of each account or fund in the property and improvements, and shall direct the proceeds to be deposited proportionally therein.