Hi, sorry to take so long to get back to you, I was not able to get on the internet.
OK, so thge questions says that the parents are 1/50 people who carry the recessive mutation, but they are only carriers , not homozygous. Therefore 1/50 people puts them at 0.02% of people that carry the mutation. You are right if both parents are carriers then they each have 50% of transmitting that information to their children and a child has 25% chance of inheriting the same mutant allele from both parents. However, you must consider the fact that each parent is 1/50 people who has the allele and therefore each parent has 0.02% chance of carrying the allele in a first place. So, what you do is you take 0.02 *0.02 (from each parent)*0.25 (chance that a child inherits mutant allele from both parents) = 0.01% chance that in withing the population the child has 0.01% chance of being a homozugous mutant. This includes the criteria that the child has both parents which have 0.02% chance each of carrying the mutant allele.
The answer is right, just the wording may be a bit confusing.
Hope this helps.