Cbetting 3 bet flops with AK? Who cbets this flop?

[Bubsy27]

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

Pre-flop: (6 players) Hero is Button with A[img]/images/graemlins/diamond.gif[/img] K[img]/images/graemlins/heart.gif[/img]
UTG folds, UTG+1 calls, <font color="#cc0000">CO raises to $4.5</font>, <font color="#cc0000">Hero raises to $17</font>, SB folds, BB calls, 2 folds.

Flop: J[img]/images/graemlins/club.gif[/img] Q[img]/images/graemlins/club.gif[/img] 6[img]/images/graemlins/spade.gif[/img] ($40, 2 players)
BB checks, Hero checks.

Turn: 9[img]/images/graemlins/spade.gif[/img] ($40, 2 players)
<font color="#cc0000">BB bets $21</font>, Hero folds.
Uncalled bets: $21 returned to BB.

Results:
Final pot: $40