Provide a detailed explanation of the impairment write-down(s) made by Qantas Group in the year ended 30 June 2021 found in annual report . Your explanation should include a discussion of:

i. the asset/s that were impaired;

ii. the type of estimations required to record the impairment;

iii. the amount of the impairment write-down; and iv. relevant disclosures in the 30 June 2021 financial report in relation to impairment testing.