Which three factors must be considered when designing a H.323 videoconferencing dial plan? (Choose three.)

A.
the number of sites in the enterprise

B.
the number and location of gatekeepers

C.
the incoming PSTN call routing method

D.
the DNs and location of conferencing MCUs to be deployed

E.
the videoconferencing features and applications to be deployed

F.
the location of voice gateways