Final answer:
Based on the ABO blood group inheritance, it is possible for Jim to be the father.
Step-by-step explanation:
The mother has blood type AB and the baby has blood type A. The possible fathers are Jim (type A) and Michael (type B). Based on the ABO blood group inheritance, it is possible for Jim to be the father. When two parents with blood types A and B have children, the children can have blood types A, B, AB, or O. Since the baby has blood type A, it is consistent with Jim being the father.