(a) All appointments to the State Highway Commission shall be made so as to assure that the commission shall be composed of:
(1) One (1) member from each of the four (4) congressional districts as the districts exist at the time of a member's appointment; and
(2) One (1) member from the state at large.
(b) The members of the commission shall each receive one hundred dollars ($100) per diem and their actual expenses while engaged in the work of the commission.