How many calls can be made?

Given a VoIP network with these attributes:
Codec: G.728
Bit rate: 16 Kbps
WAN Bandwidth: 256 Kbps
Packet Header: 6 bytes
Payload: 40 bytes
CRTP: Yes
How many calls can be made?

A.
14 calls

B.
13 calls

C.
8 calls

D.
7 calls

Explanation: