From Past History, We Know There Is a 2/3 Chance That Jane Is a Carrier of Cystic Fibrosis. Her Husband Is A?

From past history, we know there is a 2/3 chance that Jane is a carrier of cystic fibrosis. Her husband is a carrier. If she is a carrier, there is a ¼ chance that a son will have the disease. If not, a son cannot get the disease. Transmission is independent from child to child. If they have 3 sons, all of whom do not have the disease, what is the probability that she is a carrier?