In June 2017 , Ian sold a freehold building for £200,000, realising a chargeable gain of £25,000. The building had been used only for trade purposes. In July 2017, he acquired fixed plant and machinery costing £220,000 and elected that the gain on the building should be held-over against the plant and machinery. Explain the way in which the held -
over gain would be treated if:

(a) Ian sells the plant and machinery in October 2021.

(b) Ian sells the plant and machinery in March 2029.