Section 2. There shall be in the department an office of administration and an office of program planning and management, each under the supervision of an assistant secretary of elder affairs, in this chapter called an assistant secretary, subject to the direction, control, and supervision of the secretary. Each assistant secretary shall be a person of skill and experience including five years of administrative experience in the field of his appointment, shall be appointed by the secretary, and shall serve at his pleasure. The position of assistant secretary shall not be subject to chapter thirty-one and the provisions of section nine A of chapter thirty shall not apply to any person holding such appointment. Each assistant secretary shall devote his full time to the duties of his office.