Depreciation

John,

Could you please explain the answer to question 7.9 in the BPP revision kit. This is my understanding:

Plant held all year (200,000-40,000) x 20% – Since its straight line depreciation, we subtract the disposal value of the asset and then depreciate.

Additions: 50,000 x 20% x 6/12 – This is obvious

Disposal: 40,000 x 20% x 6/12 – This confuses me, why are we depreciating the disposal?

Thanks!
Rachel