The association shall provide, win, place and show pools in any race in which there are five or more separate wagering interests which are obligated to start. The association shall provide win and place pools where there are four separate wagering interests which are obligated to start. The association shall provide a win pool only in any race where less than four separate wagering interests are obligated to start. Upon a showing of good cause, the Board may waive the requirement for a place or show pool in any race.