Chapter 11.7, Problem 75PE

The blood type of an individual is classified according to the presence of certain antigens, substances that cause the immune system to produce antibodies. These antigens are denoted by $\text{A,B}$ , and $\text{Rh}$ . If an individual's blood contains either the $\text{A}$ or $\text{B}$ antigen, these letters are listed in the blood type. If neither $\text{A}$ nor $\text{B}$ is present, then the letter $\text{O}$ is used. If the $\text{Rh}$ antigen is present, the blood is said to be $\text{Rh}$ positive $\left({\text{Rh}}^{+}\right)$ ; otherwise, the blood is $\text{Rh}$ negative $\left({\text{Rh}}^{-}\right)$ . Under this system, a person with ${\text{AB}}^{+}$ blood has all three antigens, and group ${\text{O}}^{-}$ is absent all three antigens.

The distribution of blood types for people living in the United States is given in the table. Refer to the table for Exercises 75-78. Round to $3$ decimal places when necessary.

a. If an individual is randomly selected from the population, find the probability that the individual will have the $\text{Rh}$ factor,

b. If three people are selected at random, find the probability that they all have the $\text{Rh}$ factor.