capital allowances

hello…..

can anyone help me plz

i am having difficulties in understanding whether to charge the remaining balance when disposing an asset.

say a company has a high emission car in the special rate pool b/f 8000 1 april 2012
it was the only asset in the special rate pool prior to the disposal

it disposes the asset on the 30 june 2012 for 12000

what happens to the balance of 4000??? do you charge wda or you bring the 4000 to the capital allowance column

secondly if the asset is sold for say 4000? what will happen to the balance of 4000? do you calculate the wda on it or bring the 4000 in the capital allowance

can anyone help me understand the concept behind the situation plz

thanx!!!