Gstr1 by subbroker

AT THE TIME OF GSTR1 WHICH TABLE SHOULD THE SUBBROKER FILL b2c or b2b ?Please note that the sub broker is an agent pf the Main broker and the main broker collects the gst from the client along with the brokerage and  pass on 75% of the total brokeage to the subbroker alongwith proportionate GST, And the subbroker deposit the GST to the GOVT. The sub-broker is also registered in GST as he is an agent of the main broker. The main broker deposits 25% to the Govt, Is the main broker entitled to get Input tax credit. If yes , Why   If not Why?