AK after limper in 3r

[helter skelter]

PokerStars No-Limit Hold'em Tourney, Big Blind is t800 (9 handed)


antes are 75

MP3 (t12365)
<font color="#C00000">Hero (t34423)</font>
Button (t8516)
SB (t9599)
BB (t72912)
UTG (t5966)
UTG+1 (t16565)
MP1 (t17500)
<font color="#C00000">MP2 (t12723)</font>

Preflop: Hero is CO with A[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/club.gif[/img].
<font color="#666666">3 folds</font>, MP2 calls t800, <font color="#666666">1 fold</font> Hero ?

Only had about 13 hands played with villain, all I remember is his vpip was in the low 20's. How much to raise and the theory behind it?