X      
          number                         X      
         of exams                  X     X      
                                   X     X      
                       X           X     X      
                       X     X     X     X      
                 X     X     X     X     X      
           X     X     X     X     X     X     X   
         -----------------------------------------
         30-39 40-49 50-59 60-69 70-79 80-89 90-99
			   grades

	The distribution of grades for the midterm.