S. 45(4) : Capital gains-Distribution of capital asset-Dissolution of firm-Depreciable assets-Block of assets-Transfer of depreciable capital assets-Incoming partner-Liable to capital gains tax under Section 45(4), even though there was no distribution of assets among partners upon dissolution-Section 50 does not apply when asset’s value has already been taxed as capital gains under Section 45(4) [S. 2(11), 45, 50, 50A]