a) missing informations -> (female students that got a passed grade)/(total female students)
b) missing informations -> (male students that got a passed grade)/(total male students)
c) female student got a B = (female students that got a B)/(total female students) = 10/50 = 0.2
d) male student got a A = (male students that got a A)/(total male students) = 8/50 = 0.16