That depends from which station to which station do you want them. Only a few stations have quotas for First AC. Also, at the time of booking, only the word "CONFIRMED" will appear on your ticket. It is only during the preparation of reservation chart that "Coupe" or "Cabin" is assigned. As a single passenger, I have sometimes got a coupe (2-seater) or a cabin (4-seater). But, when my parents traveled, they were allotted a coupe most of the time in Rajdhani. But, its all chance. Hope this helps. All the best!