partypoker - $0.10 NL (6 max) - Holdem - 5 players
Hand converted by PokerTracker 4: http://www.pokertracker.com

Hero (BTN): $19.23
SB: $5.21
BB: $10.00
UTG: $29.05
CO: $23.38

SB posts SB $0.05, BB posts BB $0.10

Pre Flop: (pot: $0.15) Hero has Qs Qd
fold, CO raises to $0.30, Hero raises to $0.90, fold, fold, CO raises to $2.80, Hero calls $1.90

Flop : ($5.75, 2 players) 4c 9h 9d
CO bets $4.10, ?

I see this situation often. Can somebody please explain what is the most profitable line in this case, pre and postflop. We are very deep and CO is 4b for the first time (very small sample 0/4 though).