4. (l) Subject to the provisions of this Act, there shall, in respect of any business to which this Act applies, be charged, levied and paid on the amount by which the profits during any chargeable accounting period exceed the standard profits a tax (in this Act referred to as “excess profits tax”) which shall, in respect of any chargeable accounting period ending on or before the 31st day of March, 1941, be equal to fifty per cent of that excess and shall, in respect of any chargeable accounting period beginning after that date, be equal to such percentage of that excess as may be fixed by the annual Finance Act: Provided that any profits which are, under the provisions of sub section (3) of section 4 of the Income tax Act, 1922, exempt from income tax, and all profits from any business of life insurance shall be totally exempt from excess profits tax under this Act: Provided further that, in the case of any business which includes the mining of any mineral, any bonus paid by or through the Government in respect of increased output of the mineral shall be totally exempt from excess profits tax under this Act. (2) Where a chargeable accounting period falls partly before and partly after the end of March, 1941, the foregoing provisions of this section shall apply as if so much of that chargeable accounting period as falls before, and so much of that chargeable accounting period as falls after, the said end of March were each a separate chargeable accounting period, and as if the excess of profits of that separate chargeable accounting period were an apportioned part of the excess of profits arising in the whole period determined in accordance with the provisions of section 7A.