S. 11 : Property held for charitable purposes-Computation of income-Depreciation-Provision barring allowance of depreciation on asset whose acquisition treated as application of income-Prospective-Entitled to depreciation for earlier years-Provision for bad and doubtful debts and bad debts-Provision restricting allowance to debts written off applicable only prospectively-Provision reasonably made for loss or outgoing, can be deducted from income if there is apprehension that debt might become bad-Losses arising on sale of assets to be considered while computing income. [S.2 (15), 11(6), 32, 28 to 44, 45 to 48]