Are the following equally appropriate to be used at work with a colleague or client? I don't want to be informal, but I don't have to be too formal either.
Let me know when you are free so that we can discuss this in more details.
or
Let me know when you are available so that we can discuss this in more details.
or
Let me know when you are not busy so that we can discuss this in more details.
Disclaimer: I'm not a native English speaker (as if I had to explain that)