Suppose that an animal that has a system similar to ABO blood types in humans.  The ABO part is the same. In addition, they have a second independent gene that creates a mimic A protein, with alleles M ( a dominant allele that makes this A- minic protein) and a m (a recessive allele that doesnt make this mimic). When the mimic protein is expressed it adds a cell surface protein that tests as A-type in addition to whatever is expressed from the ABO locus).  Consider a cross between ABMmxBOMm  give the expected frequencies for the possible phenotypes among offspring.