A genetic population study is conducted to evaluate the penetrance of an inherited disorder characterized by impaired iron metabolism that primarily affects the liver. Affected individuals commonly develop diabetes mellitus and bronze skin pigmentation. Among 120 individuals with a family history of this disease who undergo genetic screening, 40 are found to carry the disease-causing genotype. Of these, only 10 exhibit clinical manifestations of the disorder. What is the probability that individuals with the disease-producing genotype will develop the disease phenotype?