(e)In lieu of any sum to be paid or allowed by the Contractor under clause 20 of these Conditions in respect of any period during which the Works may remain incomplete occurring after the date on which the Employer shall have taken possession of the relevant part there shall be paid or allowed such sum as bears the same ratio to the sum which would be paid or allowed apart from the provisions of this clause the Contract Price less the amount contained therein in respect of the relevant part bears to the Contract Price..