After the first semester of 6th grade, the ratio of the number of math students earning an A to the number of students earning a B was 2:9. However, after the second semester, the ratio of the number of math students earning an A to the number of math students earning a B was changed to 4:7.   How many students had a B at the end of the first semester if there were 92 students who received an A in the second semester?