An asset bought at a cost of £24 000 is depreciated using the straight-line meth od over 6 years, assum ing a resale value of £3000 at the end of that time . At the end of the third year of useful life of the asse t the written down value is:

(a) £ 13500;

(b) £ 12000;

(c) £ 11000;

(d) £ 10500.