If there is more than one * PHIIB in respect of the premium or amount, work out in accordance with section 22 - 15 the amount of each of those PHIIB's share of the PHII benefit , in respect of the premium or amount, on the following assumptions:
(a) assume that the PHIIB is the only person who is a PHIIB in respect of the premium or amount;
(b) assume that the premium or amount is the amount of the premium (or the amount in respect of the premium) divided by the number of persons who are PHIIBs in respect of the premium or amount.