Raise with A7o, BB leads into raiser on 542 flop

[betgo]

$100r, on the bubble. Villain is Annette_15.
PokerStars No-Limit Hold'em Tourney, Big Blind is t2000 (7 handed) internettexasholdem.com

SB (t14455)
BB (t62475)
UTG (t84793)
MP1 (t18194)
Hero (t66705)
CO (t32956)
Button (t7720)

Preflop: Hero is MP2 with A[img]/images/graemlins/spade.gif[/img], 7[img]/images/graemlins/club.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">Hero raises to t6000</font>, <font color="#666666">3 folds</font>, BB calls t4000.

Flop: (t10600) 4[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">BB bets t8000</font>, Hero ???