ANSWER : Group I

75 feet for 31 minutes -> Group G
Group G on the surface for 1:45 ->E
Group E at 52 feet  max time -> 20 (so 17 minutes is o.k.).  Residual Nitrogen time is 30 minutes.  Add RNT (residual nitrogen time) to ABT (actual bottom time) of 17 to get 47 minutes.

52 feet for 47 minutes ->H
H out for 2 hours ->E;    E at 44 feet can stay 32 minutes (so 26 is o.k.).  RNT is 38 minutes.  Add to actual bottom time of 26 minutes to get 64.  44 feet for 64 minutes results in group I.