If a company does charity work for another company or organization,
how much of it can be a write off?

For instance, if Company A does a service for Company B, free of
charge, how much can be a write off under the following conditions:

1. Company A can charge $10,000 for this service in the market
2. It cost Company A $5,000 to perform the service
3. Company B paid nothing for the service

Can Company A claim it gave $5000, $10000, or some other amount, for a
charitable cause?

Does Company B have to be a non profit organization or can it be any
type of company?

Thanks.