5SEach of the parties to the arbitration shall, within 28 days from the appointment of the arbiter, deliver to him a statement of that party’s case with all necessary particulars; and—
(a)no amendment or addition to the statement or particulars delivered shall be allowed after the expiration of the said 28 days except with the consent of the arbiter;
(b)a party to the arbitration shall be confined at the hearing to the matters alleged in the statement and particulars so delivered and any amendment thereof or addition thereto duly made.