Rust pop-quiz: correct pnl fee and commission computations

Rust pop-quiz

./pnl is computing fees wrongly.

Fix it.

Eheh. 😅

So, less meanly: one way to fix ./pnl is to examine the fees and commissions computations and correct those formulæ.

There's a much simpler way to fix ./pnl fees: use the spreadsheet totals as inputs.

GO TO IT!

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