Do I need to call now?

[Bobbin]

CO is totally unknown

SB ($412.45)
BB ($518.20)
UTG ($383.68)
MP ($200)
CO ($328.60)
Hero ($194)

Preflop: Hero is Button with A[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/heart.gif[/img]. SB posts a blind of $1. UTG posts a blind of $2.
<font color="#666666">1 fold</font>, CO calls $2, <font color="#CC3333">Hero raises to $9</font>, <font color="#666666">2 folds</font>, CO calls $7.

Flop: ($21) 6[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
CO checks, Hero checks.

Turn: ($21) A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
CO checks, <font color="#CC3333">Hero bets $15</font>, <font color="#CC3333">CO raises to $36</font>, Hero calls $21.

River: ($93) K[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
CO calls $328.60 (All-In), Hero ?