During the temporary absence or disability of the County Executive, the Chief Administrative Officer shall act as County Executive and may sign contracts or other legal papers or instruments which the County Executive is authorized to sign. The County Executive shall designate, in writing, a head of a county department who shall act as County Executive during the temporary absence or disability of both the County Executive and the Chief Administrative Officer. The Acting County Executive may sign contracts or other legal papers or instruments which the County Executive is authorized to sign.