Who owns the prototypes?

I was hired to create 50 schematics. They wanted them in PDF format and Word.

I asked if they wanted them in a format that would allow for changes by their own people but they said no because they didnt own the software anyway.

I delivered the completed drawings, client happy, paid bill.

They have hired a new person to do some work for them and this new person wants all of my drawings that I created in the format that would allow the drawings to be changed.

Do I give them the drawings in the format of the application I created them in or do I charge them for the ‘prototypes’ since the contract was for finished product in word/pdf format only?

Wanting to be fair but unclear as to what is ‘right’.

Would appreciate your opinions.

Thank you,

Carol

PS – I maybe should have posted this under the discussion area – sorry.