P(A)=0.2, P(A|B) = 0.3 and P(AuB)=0.6. Find i P(B) ii P(B'|A')

i. P(AuB) = P(A) + P(B) - P(AnB) 

P(AnB) = P(A|B)P(B) = 0.3P(B)

P(AuB) = P(A) + 0.7 P(B) --> 0.6 = 0.2 + 0.7 P(B) --> P(B) = 4/7

ii. P(B'|A') = P(A'nB')/P(A')

P(A'nB') = 1 - P(AuB)

P(B'|A') = 0.4/0.8 = 1/2