probability

a)P(E)= P(A can be promoted to the university if A can be promoted to the F.6)
* P(B can be promoted to the university if B can be promoted to the F.6)= (0.56 / 0.8) * (0.35 / 0.7)= 0.7 * 0.5= 0.35
b)P(E)= P(A can be promoted to the university but B cann't)
+ P(B can be promoted to the university but A cann't)= (0.7)(1 - 0.5) + (1 - 0.7)(0.5)= 0.35 + 0.15= 0.5