NL50 Flop the nut flush, get lead into on the turn. Extraction.

[JROK777]

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
6 players
Converter

Stack sizes:
UTG: $35.10
Hero: $91.55
CO: $110.90
Button: $31.20
SB: $47.15
BB: $53.90

Pre-flop: (6 players) Hero is UTG+1 with 4[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/club.gif[/img]
UTG folds, <font color="#cc0000">Hero raises to $1.75</font>, 3 folds, BB calls.

Flop: 9[img]/images/graemlins/club.gif[/img] K[img]/images/graemlins/club.gif[/img] 6[img]/images/graemlins/club.gif[/img] ($3.75, 2 players)
BB checks, <font color="#cc0000">Hero bets $3.6</font>, BB calls.

Turn: 5[img]/images/graemlins/spade.gif[/img] ($10.95, 2 players)
<font color="#cc0000">BB bets $5</font>, <font color="#cc0000">Hero raises to ???

What is the best way to play this turn? We don't want to blow villian off a draw. But we don't want to give odds to draw at boats. What play will make us the most money?