Take Apple's annual report as an example to complete the following three questions: 1. What cost allocation method did Apple adopt in 2021? 2. Has Apple's assets been impaired in 2021? Take the 2021 financial report as an example, choose the relevant data to support your judgment. 3. Does Apple adopt an asset-light model or an asset-heavy model? Take the 2021 financial report as an example, choose the relevant data to support your judgment. 4. What is three options for companies to implement the light asset model? According to the annual reports of Apple in 2020 and 2021, which of the asset light models did Apple adopt?