(2) Where in the case of an assessee, being a non-resident Indian,—

(a)  the gross total income consists only of investment income or income by way of long-term capital gains or both, no deduction shall be allowed to the assessee under Chapter VI-A and nothing contained in the provisions of the second proviso to section 48 shall apply to income chargeable under the head "Capital gains";

(b)  the gross total income includes any income referred to in clause (a), the gross total income shall be reduced by the amount of such income and the deductions under Chapter VI-A shall be allowed as if the gross total income as so reduced were the gross total income of the assessee.