A technician is installing an Avaya CallPilot RIs. 5.0 system with 32 Voice channels, eight Fax channels, and four automated speech recognition (ASR) channels using an Avaya CallPilot 600r server and a Meridian 1 IP Enabled (IE) Option 61C switch. How many NTRB18CA MGate cards must be installed in the switch to support this configuration?