Analyzing the operating cash flow of apple in 2019.

This report is 2019 annual report , if information is missing, you can find from

https://investor.apple.com/investor-relations/default.aspx

Analyzing the change of Depreciation and amortization/ Other/ Accounts receivable, net/ Accounts payable/ Deferred revenue/ other current and non- current liability, and make simple explanations for each change, and have a overall conclusion for the operating cash flow.