(b)if at any time before the expiry of ten years from the end of the previous year in which the ship or aircraft was acquired or the machinery or plant was installed, the assessee does not utilise the amount credited to the reserve account under sub-section (4) for the purposes of acquiring a new ship or a new aircraft or new machinery or plant [other than machinery or plant of the nature referred to in clauses (a), (b) and (d)] [of the second proviso] [ Substituted by Act 3 of 1989, Section 6, for " the proviso" (w.e.f. 1.4.1989).][to sub-section (1) for the purposes of the business of the undertaking; or [Inserted by Act 66 of 1976, Section 8 (w.e.f. 1.4.1976).]