15. Where a contract is with two or more individuals practising in partnership—
(a)the contract is to be treated as made with the partnership as it is from time to time constituted, and the contract must make specific provision to this effect; and
(b)the terms of the contract must require the contractor to ensure that any person who becomes a partner in the partnership after the contract has come into force is automatically bound by the contract whether by virtue of a partnership deed or otherwise.