21. Where the claimant occupies a dwelling as the claimant’s home and the claimant provides in that dwelling board and lodging accommodation, an amount, in respect of each person for whom such accommodation is provided for the whole or any part of a week, equal to—
(a)where the aggregate of any payments made in respect of any one week in respect of such accommodation provided to such person does not exceed £20, 100% of such payments; or
(b)where the aggregate of any such payments exceeds £20, £20 and 50% of the excess over £20.