John purchased new machinery for his small business factory on 1st June 2018 for $8,000. The effective life of the machinery is determined to be five years. John sold his old business machinery for $4,000 on 31 August 2019. John used this machinery 90% for business purposes. With reference to the relevant legislation and case law, discuss the tax consequences arising from the disposal of the old machinery under the prime cost method. (Taxation Law Question)