a=0.35, b=0.5, eigenvectors(({{1 - a, 0, (1 - a) b, 0}, {a, 0, a b, 0}, {0, 1 - a, (1 - a) (1 - b), (1 - a) b }, {0, a, a (1 - b),1- (1- a)b}}))