PokerStars No-Limit Hold'em, $0.50 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

BB ($50.60)
UTG ($39.30)
MP ($102.10)
Hero ($105.30)
Button ($66.65)
SB ($29.45)

Preflop: Hero is CO with A, A.
2 folds, Hero raises to $1.75, Button calls $1.75, 2 folds.

Flop: ($4.25) Q, 6, 9 (2 players)
Hero bets $3, Button calls $3.

Turn: ($10.25) 6 (2 players)
Hero bets $7, Button calls $7.

River: ($24.25) K (2 players)
Hero ???

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Villian is 12/2/0.6 through 40 hands.

What's your river move here?