Partner stands on extension of player's line of play behind the ball

A and B are partners in a four-ball competition. A’s ball is on the putting green 30 feet from the hole, and B’s ball is 20 feet from the hole on a similar line. To assist him with his own putt, B stands on an extension of the line of putt behind A’s ball while A putts. What is the ruling?

A was in breach of Rule 14-2b by putting with his partner, B, positioned on or close to an extension of the line of putt behind the ball. As A’s breach assisted B, B also incurred the same penalty (Rules 30-3f and 31-8).

In match play, Side A-B loses the hole.

In stroke play, A incurs a penalty of two strokes and B incurs the same penalty.