What is the minimum recommended dBm when designing a VoIP network with 11-Mbps cells, and no more than one access point per overlapping channel set?

What is the minimum recommended dBm when designing a VoIP network with 11-Mbps cells, and no more than one access point per overlapping channel set?

A.
-35

B.
-56

C.
-67

D.
-86