Churchill Downs will offer a bet on the four night racing cards of its upcoming spring meet that will require bettors to pick the winners of 10 races in a row, company officials said Wednesday.\r\nThe bet, which will have a 10-cent minimum, will present one of the most daunting challenges to bettors on the national wagering landscape. If no one correctly selects 10 winners, 75 percent of the net pool will be carried over to the next time the bet is offered, with 25 percent being distributed to the player or players who have &ldquo;selected the first-place finisher in the greatest number of pick-10 contests,&rdquo; according to regulations approved by the Kentucky Horse Racing Commission on Wednesday.\r\nChurchill is scheduled to hold its first night-racing card on opening day, April 30. The other three night-racing dates, all on Fridays, are June 17, June 24, and July 1.\r\nEkumene Lysonge, Churchill&rsquo;s vice president of regulatory and government relations, said that the track decided to limit the wager to the night-racing cards as a way to draw attention to the track&rsquo;s product in the night-time market. Churchill launched night racing in fall 2009 and installed permanent lights last year.\r\nThe wager has similar rules to the pick six in most racing jurisdictions. In the event of a scratch after the first leg is run, the bettor will receive the post-time favorite. If a race is moved off the turf after the first leg has been run, bettors will receive the &ldquo;all&rdquo; selection for the race.