Based on the analysis of the text, it is difficult to determine with certainty whether the above text was written by AI or a human. However, there are some indications that suggest a combination of both AI and human input.

Lines that are likely written by AI: - The calculations and numerical values provided in the text, such as the cash flow forecast, total purchasing power, share count, total return, etc., seem to be generated by an AI algorithm. - The explanation of margin accounting principles and the calculation of equity, maintenance margin, and margin call requirements also appear to be generated by AI.

Lines that are likely written by a human: - The introduction and conclusion sections, which provide a narrative and analysis of Dave’s situation, seem to be written by a human. - The discussion of Dave’s choices, the reasons for his losses, and the analysis of his returns appear to be written by a human.

It is difficult to determine the exact percentage of the text that is written by AI and human, but it seems that a significant portion of the numerical calculations and explanations are generated by AI, while the narrative and analysis sections are likely written by a human.