In order to help new students in selecting better teachers, current students at a college rate their professors' teaching ability either as Excellent, Good or Poor. Professor Crane's ratings by 140 students from winter, summer and fall last year are presented in the chart below:

30 25 25 21 20 20 15 Excellent 14 Number of Students 15 14 Good 12 11 Poor 10 8 Winter Summer Fall