Please help with simple PA system

[bellaroxio]

Hi there. Hope you experts can help. I have never done a PA system. My background is high-end home stereo system. One of my dear dear dear customer wants me to install an reliable commercial PA system that would be used 18 hours a day.
His office as 3 areas: A, B, and C
Each area is no bigger than 20'x6'
He wants to do the following:
A can talk to B, C, or Both
B can talk to A, C, or Both
C can talk to A, B, or Both

I was thinking of using DBX ZC3, gooseneck microphone, DBX Zonepro 641m and (2) 8 ohm speakers at EACH LOCATION. I am lost at what amplifier to use.

What would you recommend? Which goosenect microphone? Which amp? Any other system? Thanks so so so much.