(a) the amount of income-tax calculated on income from units of an open-ended equity oriented fund of the Unit Trust of India or of a Mutual Fund, at the rate of ten per cent; and

(b) the amount of income-tax with which the assessee would have been chargeable had his total income been reduced by the amount of income referred to in clause (a)

(2) Nothing contained in sub-section (1) shall apply in relation to any income from units of an open-ended equity oriented fund of the Unit Trust of India or of the Mutual Fund arising after the 31st day of March, 2003.