In last week's quiz, we learned that a batter's time at-bat ends when he becomes a batter-runner -- and the next batter in the lineup is then expected to come to the plate. In last week's quiz, B1 ended the inning with a base-on-balls while at the same time his teammate (R2) was retired for the 3rd out of the inning. B2 should lead-off the next inning, but B1 mistakenly thinks that he did not complete his time at-bat.

 

When B1's team returns to bat the next inning, instead of B2 batting, B1 bats and singles. After B1 arrives at first base, the defensive coach calls "time" and tells the plate umpire that he thinks B1 was not the proper batter. The coach is correct (B2 should have batted). Now what does the umpire do?