25NL AK TPTK gets raised on turn - standard fold?

[jimpo]

Full Tilt No-Limit Hold'em, $0.25 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

BB ($23.10)
Hero ($27)
MP ($9.50)
CO ($25.40)
Button ($18.95)
SB ($28.15)

Preflop: Hero is UTG with K[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Hero raises to $0.85</font>, <font color="#666666">1 fold</font>, CO calls $0.85, Button calls $0.85, <font color="#666666">2 folds</font>.

Flop: ($2.90) K[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets $2.2</font>, CO calls $2.20, Button folds.

Turn: ($7.30) J[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $4.4</font>, <font color="#CC3333">CO raises to $13</font>, Hero...?

Villain is unknown, no reads. What's the action?

What range do you see CO having?

If you fold, what kind of reads/stats would you have to have to do something else?