In a Certain Class,40% of Students Had a B Average

Essay

In a certain class,40% of students had a B average at midterm.Of these,50% ended up with a course grade of B.Of those who did not have a B average at midterm,40% ended up with a course grade of B.If one of the students in the class is selected at random and is found to have received a B for the course,what is the probability that the student did not have a B average at midterm?