How to calculate ABV after adding late editions

[H0U5ECAT]

How can I work out my final Alco content in this beer I'm doing?
I'm brewing a porter and adding some fruit post initial fermentation in the secondary.
OG is 1.052
The original recipe brings the porter in at FG 1.012. giving it an ABV of 5.25%
I'm adding 1.5 kg of cherries (compote with vanilla and coconut) at secondary.
This is obviously going to change all my readings, so when I come to bottle it, how am.i going to know my actual final? I'm sure there's some extra math in there somewhere

 

[MHB]

Bit of a piece of string question.
When you say 1.5kg of cherries is that fresh whole cherries, sweet or sour cherries with or without pits.
With a bit more information you could make a stab at how much extra sugar you are adding.
But a way to work out exactly what you are going to get is nearly impossible, mainly because the sugars in the fruit wont all go into solution at once, if we were talking about a known weight of sugar or a sugar that was entirely soluble you could just measure the gravity before and after the addition. Keep track of the changes in gravity just like some do with big Belgians.
Mark

 

[H0U5ECAT]

Cheers.
So to follow up from these questions...
Frozen pitted cherries, coconut chips, vanilla bean paste.
I'm making a compote from these. I won't go into that particular detail at this time.
The process for adding these will be adding the compote to the secondary.
I'll be transferring to secondary after my FG stops and is stable for a couple of days. This will give me my standard ABV (a).

After adding the compote, I'll do a new reading and this will give me a new OG (b).
The yeast is going to be woken up again with the new additive and do it's thing again and thus increase the ABV even further (C).

I'm sure I'm not the first person ever to ask this and there must be some kind of formula to work out the new numbers.

I'm not concerned about knowing the sugar content of the compote because this isnt what I'm trying to measure.

However, I did find this on line as a rough guide for adding fruits to beer...
https://byo.com/article/brewing-with-fruit-techniques/
Cherries have about a 14% sugar content. Fyi.