Answer:
Make a Punnett Square. (: You do not know if the mother is heterozygous or homozygous for type A, though, so you'll probably have to make 2.
If the mother was homozygous..
A A
A AA AA
B AB AB
50% chance of Type A and 50% chance of type B.
If the mother was heterozygous.
A O
A AA AO
B AB BO
Here there is a 25% chance of type A (homozygous), a 25% chance of AO (heterozygous but still type A), 25% chance of AB (codominance), and a 25% chance of BO (Heterozygous, but type B).