#### Answer

a) 0.9996
b)0.999992

#### Work Step by Step

a) We can use the multiplication rule: P(at least one doesn't fail):1-P(both fail) =$1-0.02^{2}=0.9996.$
b) We can use the multiplication rule: P(at least one doesn't fail):1-P(all three fail) =$1-0.02^{3}=0.999992.$