Should I install the xmrig to each PC or should I try to make one "superPC" out of them?

As we all know, GPU mining is much more profitable than CPU mining.
However, let's say I have access to 15 office PCs sitting idle for most of the day.

What coin would you suggest for CPU mining?
Is there any mining SW that could be used to combine their power?
What would you do with such HW?