606.6a.

A player who is dissatisfied with his or her initial hand may mulligan. First, the starting team takes any mulligans. For a team to take a mulligan, each player on that team decides whether to shuffle his or her hand back into the deck and then draw a new hand of seven cards. All players on that team who chose to do so take their mulligans at the same time. After each player on that team who took a mulligan looks at his or her new hand, the team repeats the process, resulting in a hand of one fewer card each time, until the hand size reaches zero cards. Teammates may consult during this process, but a player can't see the result of his or her teammate's mulligan before deciding whether to take a mulligan at the same time. Once a player has decided to keep a hand, those cards become his or her opening hand. That player can't take any more mulligans, but his or her teammate may. Once each player on the starting team decides to keep an opening hand, the other team may take mulligans.