Quote to do sound editing

Hi all,


I am asked to do the sound editing / sound design on a 26 minutes documentary on world war 1.
The film has a bunch of archives elements with no sound on which I will have to look for historic sounds (weapons, ...).
The producer wants me to give him a quote for the job.
Difficult thing to do for me as I have no idea how much time it will take me to find the appropriate sounds and edit them to the picture.

How can I make my quote ? is there any "rule" ?
Can you share your experiences ?
Should I charge the producer for my research time o just the sound editing time ?
Should I charge the producer if I have to buy specific sounds ?

Thanks for your time.

All the best from Belgium.

Pascal