Blinds are 150/300 at a 5 person table.
I have Ace

Jack

in the big blind position.
First to act folds, second to act is our chip leader who has been raising 75% of all pots before the flop and winning, he goes all in for about 6 grand.
Folds around to me...I am about 3rd at the table in chips, but still about 1/3 of what the leader has. Big blind off $300 already committed.
What would you do?
Seems like an easy decision to me but I want some other opinions.