Suppose that in Guinea pigs the ABO blood types are determined like in humans, where IA and IB codominant to each other and i (blood type O) is recessive to both. During a set of routine crosses you notice something unusual: Repeated matings between a certain female with blood type AB and a certain male with blood type A produces F1 Guinea pigs of all four blood types in the following ratios: 5A : 2B : 4AB : 1O. The genotypes of the parents are most likely: