The aggregate of the amounts of the standard rateborne expenditure of elementary education authorities in the county ascertained under the last foregoing paragraph shall be deemed to be the total rate charge of the county for elementary education for the standard year, and the Minister shall ascertain the amount in the pound of the rate which would have been required by precept of the county council to be levied by rating authorities for the purpose of meeting that charge if it had fallen to be borne by that council as part of their expenses for general county purposes.