Year end stock sheets had been incorrectly added resulting in the closing stock at 31 December 1983 being recorded as £ 12864 rather than £21 864.

The effect of the error would be:

(a) overstate profit for 1983 and 1984 by £9000 ;

(b) understate profit for 1983 and 1984 by £9000 ;

(c) overstate profit for 1983 by £9000 and understate profit for 1984 by the same amount;

(d) understate profit for 1983 by £9000 and overstate profit for 1984 by the same amount.