A National Football League coach is permitted to initiate 2 challenges to referee calls per game (outside the final 2 min. in each half). During a challenge, the referee reviews the play in question on replay monitor on the field, and the play either stands or the challenge is upheld. The National Football League reports that the time required for coach's challenge is less than 5 min. A sports statistician would like to check this claim. Describe a method for obtaining a simple random sample of challenges during NFL games.