AK Unknown villian. 100NL

[Hince]

Unknown villian. This seems like a basic spot but I am really confused without any reads... I'm not sure what the standard line is at this level.
PokerStars No-Limit Hold'em, $1.00 BB (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Hero ($98.50)
MP ($104)
Button ($103.50)
SB ($138.75)
BB ($113)

Preflop: Hero is UTG with K[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/club.gif[/img].
<font color="#CC3333">Hero raises to $4</font>, <font color="#666666">1 fold</font>, Button calls $4, <font color="#666666">2 folds</font>.

Flop: ($9.50) 3[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $7</font>, <font color="#CC3333">Button raises to $20</font>, Hero calls $13.

Turn: ($49.50) J[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">Button bets $34</font>, Hero calls $34.

River: ($117.50) 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">Button bets $45.5 (All-In)</font>, Hero folds.

Final Pot: $72