What is the probability that these two parents can have an unaffected child if the trait is autosomal dominant?

One parent is unaffected so her genotype is aa. The other parent has a 1/4 chance being homozygous dominant (AA) or a 1/2 chance of being heterozygous dominant(Aa). I realize that if the parent is AA there is a 0% chance of a normal child and a 50% chance if parent is Aa. I am just not sure how to combine all those number to get one total probability.What is the probability that these two parents can have an unaffected child if the trait is autosomal dominant?
The question is stated in a contradictory manner. You're throwing 2 possible sets of parent into it, and trying to come up with one number.





AA x aa = 100% affected





Aa x aa = 50% affected





Total probability = 0.5, since (1)(0.5) = 0.5





Is this connected at all with the question???