($22) JJ on a "safe" board, size of bet?

[1C5]

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

Button (t830)
SB (t682)
BB (t785)
UTG (t1020)
UTG+1 (t870)
UTG+2 (t800)
MP1 (t685)
MP2 (t793)
Hero (t775)
CO (t760)

Preflop: Hero is MP3 with J/images/graemlins/diamond.gif, J/images/graemlins/spade.gif.
<font color="#666666">1 fold</font>, UTG+1 calls t15, <font color="#666666">2 folds</font>, MP2 calls t15, <font color="#CC3333">Hero raises to t75</font>, <font color="#666666">4 folds</font>, UTG+1 calls t60, MP2 calls t60.

Flop: (t250) 2/images/graemlins/spade.gif, 2/images/graemlins/heart.gif, T/images/graemlins/spade.gif <font color="#0000FF">(3 players)</font>
<font color="#CC3333">UTG+1 bets t15</font>, MP2 calls t15, <font color="#CC3333">Hero raises to ?

What raise do you like here and why?

[Scuba Chuck]

You want to bet an amount that threatens your opponents stack.