Mo. Rev. Stat. § 355.456

Any contract or other instrument in writing executed or entered into between a corporation and any other person is not invalidated as to the corporation by any lack of authority of the signing officers in the absence of actual knowledge on the part of the other person that the signing officers had no authority to execute the contract or other instrument if it is signed by any two officers in category 1 or by one officer in category 1 and one officer in category 2. Category 1 officers are the presiding officer of the board and the president. Category 2 officers are a vice president, the secretary, treasurer and the executive director.