Human blood may contain either or both of two antigens, A and B.Blood that contains only the A antigen is called type A, blood that contains only the B antigen is called type B, blood that contains both antigens is called type AB, and blood that contains neither antigen is called type O.A certain blood bank has blood from a total of 1500 donors.Of these, 713 have type O, 550 have type A, 156 have type B, and 81 have type AB .

a)What is the probability that a randomly chosen blood donor has type B blood?Round to three decimal places.

b)What is the probability that a randomly chosen blood donor does not have type AB blood?Round to three decimal places.