$3\$5 live game
Hero ($2100) EP opens 9d8d $20, get 4 callers.
Flop ($100) Ad9c9h
I check, other 4 check.
Turn ($100) Ad9c9h8c
Hero bets $60, mp calls, btn calls, other 2 fold.
River ($280) Ad9c9h8c7h
Hero ($2020) bets $200
Mp ($1800) raises to $800
Btn ($4k) all in
Hero 9d8d ???

Both players are recreational, MP pretty loose aggro putting him on a hand like JTo. Does btn always have A9 here? Maybe half combo slow played AA?.3 combos A9. 1 combo 98. 1 combo 97s? I guess more combos if btn plays 97o and 98o type hands. Really deep 400bb effective so its not unlikely he folds all these hands.

What would you do? Call or fold?