http://dsc.discovery.com/fansites/cashcab/video-quiz.html
Complete the the “Cash Cab Video Quiz” and submit your entry. Entrants are required to play the game through to completion to receive a Sweepstakes entry. Entrant’s score has no bearing on whether he/she will receive a sweepstakes entry. If you do not complete the game, you will be allowed to try again until you do so successfully.
Note that there is a limit of max four entries per person/email address per day.
PRIZE: On or about September 10, 2012, the Promotion Administrator will conduct a random drawing from among all eligib1le entries received to award one (1) Grand Prize: $5,000 American Express Gift Card.