Did you know that the Ganga & Kaveri rivers are connected? ... by Mysore Varanasi Express - Vishwanath Joshi

Normally in 3 AC there are 8 compartment and each of 8 seats (3 +3 +2) i.e total 64. where as a sleeper has 9 compartment and each of 8 seats (3 +3 +2) i.e total 72.
Our past railway minister made some changes to add a side birth making 3 AC with 8 compartment and each of 9 seats (3 +3 +3) i.e total 72. where as a sleeper has 9 compartment and each of 9 seats (3 +3 +3) i.e total 81.
Where as in Garibrath there are coaches AC...
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which has 9 compartment and each of 9 seats (3 +3 +3) i.e total 81 or 9 compartment and each of 8 seats (3 +3 +2) i.e total 72. one can experience such setup in Mumbai-delhi garib rath. I do no understand if all pesenges pay same faire in a trian like garib rath, then why some have 2 side births and some have to squeeze in 3 side births.
Now going with the smae patern what is duronto 3 AC economy.
its it
8 compartment and each of 9 seats (3 +3 +3) i.e total 72?
9 compartment and each of 8 seats (3 +3 +2) i.e total 72?
9 compartment and each of 9 seats (3 +3 +3) i.e total 81?