Flopped set, boat on river, how much do you bet?

Very first hand of 20+2 PP MTT

Party Poker No-Limit Hold'em Tourney, Big Blind is t15 (10 handed) FTR converter on zerodivide.cx

UTG (t1000)
UTG+1 (t1000)
UTG+2 (t1000)
MP1 (t1000)
MP2 (t1000)
MP3 (t1000)
CO (t1000)
Hero (t1000)
SB (t1000)
BB (t1000)

Preflop: Hero is Button with 3[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/diamond.gif[/img].
UTG calls t15, UTG+1 calls t15, <font color="#666666">3 folds</font>, MP3 calls t15, <font color="#666666">1 fold</font>, Hero calls t15, <font color="#666666">1 fold</font>, BB checks.

Flop: (t82.50) K[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
BB checks, UTG checks, UTG+1 checks, <font color="#CC3333">MP3 bets t75</font>, Hero calls t75, BB folds, UTG folds, UTG+1 folds.

Turn: (t232.50) 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP3 bets t55</font>, <font color="#CC3333">Hero raises to t175</font>, MP3 calls t120.

River: (t582.50) 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
MP3 checks, Hero ?


How much do you bet on this river? Also, lets say you know he has KQ, how much do you bet now?