(1) For the purposes of determining a person's liability in respect of self-employment contributions, voluntary contributions or optional contributions payable in accordance with the Principal Act for the period commencing on 6 April 2001 and ending on 31 December 2001 -

(a) sections 18(1) (a), (c) and (h) (in so far as they apply to self-employed contributors) (as amended in each case by section 9 of this Act), and section 23(1) (as amended by section 11 of this Act) of the Principal Act shall have effect as if for each sum specified therein there were substituted £148, and

(b) section 18(1) (b) of the Principal Act shall have effect as if for the sum specified therein there were substituted £91.76.

(2) For the purposes of determining a person's liability in respect of voluntary contributions or optional contributions payable in accordance with the Principal Act for the period commencing on 1 January 2002 and ending on 31 December 2002 -