4. In a case to which paragraph 3 applies the amount of the extended payment (severe disablement allowance and incapacity benefit) shall be the lesser of—
(a)the amount required to discharge such part of the liability for council tax for the period specified in regulation 61(6)(a), less, in a case where the rebate to which paragraph 2 refers was subject to any deductions in relation to non-dependants pursuant to regulations 57(1) and 58, the amount of those deductions; or
(b)the amount of extended payment (severe disablement allowance and incapacity benefit) calculated in accordance with paragraph 2.