Genetic question

Question

Both Mrs. Smith and Mrs. Jones had babies the same day in the same hospital. Mrs. Smith took home a baby girl, whom she named Shirley. Mrs. Jones took home a baby girl, whom she named Jane. Mrs. Jones began to suspect, however, that her child and the Smith baby had been accidentally switched in the nursery. Blood tests were made: Mr. Smith was type A; Mrs. Smith type B' Mr. Jones type A; Mrs. Jones type A; Shirley type O; Jane type B. Had a mixup occured? Why did you answer the way you did?

Answer 1

http://www.paternityangel.com/Articles_zone/Blood/BloodType2.htm

Answer 2

im not paying lol ...