Equipment purchased on I Januar y 1981 for £40000 was sold on 31 December 1983 for £21000. Depreciati on had been charged on a double-declining balance basis, on the assumption of an estima ted useful life of eight yea rs. Th e total depreciation expense for 1983, including any adjustment for the 'loss' or 'gain' on disposal of the equipment was:

(a) £1500 debit ;

(b) £4000 debit;

(c) £1000 credit;

(d) £4125credit.