AA Facing CRAI on Flop - How often do we call here?

[Roadstar]

No solid reads, its a 100NL 5 max table 4 handed.

Villain seems loose but only over 25 hands, haven't seen him go crazy postflop yet. (VPIP of like 40-50%)

Paradise Poker
No Limit Holdem Ring game
Blinds: $0.50/$1
4 players
Converter

Stack sizes:
Hero: $87.90
Button: $398.55
SB: $239.75
BB: $141.00

Pre-flop: (4 players) Hero is UTG with A[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/diamond.gif[/img]
<font color="#cc0000">Hero raises to $4</font>, 2 folds, BB calls.

Flop: 9[img]/images/graemlins/club.gif[/img] 5[img]/images/graemlins/heart.gif[/img] 7[img]/images/graemlins/diamond.gif[/img] ($8.5, 2 players)
BB checks, <font color="#cc0000">Hero bets $8</font>, <font color="#cc0000">BB raises all-in $137</font>, How Often Does Hero Call here?

Range is pretty wide, villain could have overpair (JJ-KK), set, two pair, OESD, flopped straight etc.

what % of the time should we be calling against relative unknown 4 handed?

Thanks