I'm not quite sure what is bc.a, assuming that it is OBC, here's the cut-off.

The last type of cut off is actually the closing rank. The AIIMS MBBS 2018 Minimum Qualifying Marks are as follows: According to the information brochure of AIIMS MBBS 2018, the cut off for General Category is 50%. The same for SC / ST Category is 40% and the same for OBC Category is 45%. 

Speaking about cut-off ranks for OBC category in AIIMS:

1. New Delhi: 236

2. Jodhpur: 958

3. Patna: 2048

4. Bhopal: 1516

5. Rishikesh: 1664

6. Raipur: 2074

7. Bhubaneswar: 1453

8. Nagpur: 2168

9. Guntur: 2212