I am an accountant and there is a flaw in your logic. Tax losses merely reduce the liability eg they are usually a balance sheet entry only so do not affect P&L .
In the past I have taken margin averages but found that can be a bit misleading . There is an overhead burden in the costs which might have a step change impact at various levels of activity .The margin % age is an indication , but remember that there are fixed costs that the revenue must cover before an EBIT margin arises .
Good to see you trying to work it out .
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