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ID86-Simultaneous Call One for Mah Jongg and One for an Exposure
Question: If one player calls a tile and then another player declares Mah Jongg, who gets the tiles?
Answer: When a person picks a tile from the wall, and declares Mah Jongg, and another player calls for an exposure, the player who has called for Mah Jongg takes precedence.
Source: Mah Jongg Made Easy 2020 page 20 #13 [c]