(1) Every local authority which, immediately before the 1st day of July, 1977, was a public assistance authority shall pay to the health board in whose functional area the functional area of the local authority is included in respect of each year a sum representing -
(a) the total expenditure by such local authority on home assistance in the year ending on the 31st day of December, 1975, and
(b) a proportion of 40 per cent. of the amount by which the total expenditure by all health boards on supplementary welfare allowance in the year for which payment is due exceeds the total expenditure by all local authorities on home assistance in the year ending on the 31st day of December, 1975, the said proportion of 40 per cent. payable by such authority being that which the total expenditure on home assistance by that authority in the year ending on the 31st day of December, 1975, bears to the total expenditure by all local authorities on such assistance in that year.
(2) In determining t