Subject: mathqa
Question: the probability that event a occurs is 0.4 , and the probability that events a and b both occur is 0.45 . if the probability that either event a or event b occurs is 0.6 , what is the probability that event b will occur ?
Option: 
A: 0.05
B: 0.55
C: 0.5
D: 0.45
Answer: B