4.24 Sickle cell anemia:  Sickle cell anemia is a genetic blood disorder where red blood cells lose their flexibility and assume an abnormal, rigid, "sickle" shape, which results in a risk of various complications. If both parents are carriers of the disease, then a child has a 25% chance of having the disease, 50% chance of being a carrier, and 25% chance of neither having the disease nor being a carrier. If two parents who are carriers of the disease have 3 children, what is the probability that

(a) exactly two will have the disease?
(please round to four decimal places)

(b) none will have the disease?
(please round to four decimal places)

(c) at least one will neither have the disease nor be a carrier?
(please round to four decimal places)

(d) the first child with the disease will be the third child?
(please round to four decimal places)