First calculate the probability of type AB, which is the remainder after subtracting types A, B and O.
P(AB) = 1-(0.34+0.12+0.5) = 1-0.96 = 0.04
Anti-b will react with types B and AB, so
P(reaction) = P(B)+P(AB) = 0.12 + 0.04 = 0.16
Answer: For this person, the probability of reaction with anti-b is 0.16
