On Monday bankrupt car-rental company Hertz filed to sell up to $500 million in new shares.br Business Insider reports the stock fell nearly 25 in premarket trading Monday.br The move comes just after Hertz shares surged nearly 70 Friday when the company won bankruptcy court approval to sell up to $1 billion in new shares.br Hertz warned the new common stock could "ultimately be worthless" due to their bankruptcy proceedings.