What is the percentage chance of having an unaffected baby, when both parents have achondroplasia?

Achondroplasia is an autosomally dominant inherited disorder. In the question, both the parents are having an autosomal dominant disorder. For the child to be unaffected he should inherit two normal alleles. According to the autosomal dominant inheritance pattern the chances of having an unaffected baby is 25%. Ref: Robbins Pathologic Basis of Disease, 6th Edition, Page 1220