100NL River bet size

[kitaristi0]

Villain is loose calling station, like 50/4/1 or something. His flop call means he has two cards. His turn call probably means he has something.

What do I bump it to on the river? I think I already know what I should've raised, but I wanna hear what you think.

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.50/$1
6 players
Converter

Stack sizes:
UTG: $165.55
UTG+1: $56.55
CO: $248
Button: $120.55
Hero: $143.50
BB: $69.05

Pre-flop: (6 players) Hero is SB with A[img]/images/graemlins/heart.gif[/img] 9[img]/images/graemlins/spade.gif[/img]
UTG calls, 3 folds, Hero calls, BB checks.

Flop: Q[img]/images/graemlins/heart.gif[/img] 9[img]/images/graemlins/diamond.gif[/img] 9[img]/images/graemlins/club.gif[/img] ($3, 3 players)
<font color="#cc0000">Hero bets $3</font>, BB folds, UTG calls.

Turn: 8[img]/images/graemlins/heart.gif[/img] ($9, 2 players)
<font color="#cc0000">Hero bets $7</font>, UTG calls.

River: A[img]/images/graemlins/spade.gif[/img] ($23, 2 players)
<font color="#cc0000">Hero bets $12</font>, <font color="#cc0000">UTG raises to $24</font>, <font color="#cc0000">Hero raises to ?