What is the recommended minimum speed at the edge of the cells in an 802.11g network for a good Cisco VoWLAN deployment?

What is the recommended minimum speed at the edge of the cells in an 802.11g network for a good Cisco VoWLAN deployment?

A.
11 Mb/s

B.
18 Mb/s

C.
24 Mb/s

D.
54 Mb/s