The Lead of Team B should place the mat and redeliver the jack, and have it centred, but should not play the first bowl.
Law 33.1.1.1 If a jack in its original course is displaced by a member of the team that delivered the jack, the opposing lead should place the mat as described in Law 19.1.1 and redeliver the jack, making sure that it is centred, but should not play first.
Law 19.1.1 – Before the start of play in each end, the player to play first should place the centre line of the mat lengthwise along the centre line of the rink, with the mat line at least 2 metres from the rear ditch and at least 25 metres from the front ditch.
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