Laying freebet on parlays- calculator

Rookie here, please bear with me.

The offer is bet €100 on a treble with minimum 3 selections and receive a €100 freebet. I will have 3 X 1.95 selections in this treble.

I like to lay the selections in the original €100 bet. (5% juice on each selection).

Then I think to use the freebet on a 8-10 oddser and lay the selection in that one too.

In my head I will lose between €5 and €20 on the original bet, depending on which selection that lose.
On the freebet however I struggle to see how much I will be left with and what my net profit from this offer will be.

Do you know of a very simple calculator I can use?
 
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