Payment to a person by virtue of article 66 shall be the sum of -

(a) an amount if any, calculated by multiplying the arrears due for the period of 12 months from the date of commencement of the relevant period by the inflation factor, plus

(b) an amount if any, calculated by multiplying the arrears due for each calendar quarterly period or part of a quarterly period thereafter, where the period occurs prior to 1 January 1997, by the inflation factor, plus

(c) an amount if any, calculated by multiplying the arrears due for each calendar month thereafter, where the period occurs on or after 1 January 1997, by the inflation factor.