(3)(a)In case of any block of assets, deduction in respect of depreciation shall be such percentage of its written down value, as may be prescribed;(b)when any building, machinery, plant or furniture is partly, or not wholly and exclusively, used for the purposes of the business or profession, the deduction under clause (a) shall be restricted to the fair proportionate part thereof as determined by the Assessing Officer, having regard to the usage of such building, machinery, plant or furniture for the purposes of the business or profession;(c)when deduction of actual cost in respect of any machinery or plant has been allowed under section 54, no deduction under this sub-section shall be allowed.
