Midterm class performance based on grades
of Qz1 (120pts max) and Ex1 (307pts max)

Let G = Qz1 + Ex1

 350 <=G          : A
 300 <=G <  350   : B+
 250 <=G <  300   : B
 170 <=G <  250   : C+ or C
       G <  170   : D  or F