TULSA – Dollar Thrifty Automotive Group Inc. on Wednesday said underwriters have exercised an option to purchase an additional 862,500 shares of common stock for $19.25 per share. Including the option, Tulsa-based Dollar Thrifty sold 6,612,500 shares through the offering. Dollar Thrifty expects to use the $120 million in proceeds for general corporate purposes. Goldman, Sachs & Co. and J.P. Morgan Securities Inc. served as joint book-running managers for the offering. Dollar Thrifty Automotive Group operates Dollar Rent A Car and Thrifty Car Rental.