I want to use a third party software C-library "A" commerially in a product "P" (in fact a firmware, running on a device).
The third party product "A" is subject to Apache 2 license. That means, I have to give a notice to the user of the final product "P" about using this open source library.
Now I have a third library "C" from a company (in fact it is a driver for a part of a microcontroller. We are allowed to use "C" internally for developing "P". We are not allowed to give away "C" to anybody else, beside of the object code generated.
Question:
Is it allowed to make adaptations of "A" in a way to call functions of "C" within "A" ?
We do not need to make our changes of "A" public, but can there be a problem?