(a) One-half of the members of the Improvements Committee shall retire at noon on the first day of April every year.
(b) The members who shall retire one year after the Improvements Committee is constituted under section 49B shall be selected by lot at such time previous to the first day of March immediately preceding and in such manner as the Chairman may determine.
(c) During the succeeding years, the members who shall retire under this section shall be the members who were longest in office: