Blood type AB is the rarest blood type, occurring in only 4% of the population in the United States. In Australia, only 1.5% of the population has blood type AB. Suppose a random sample of 50 U. S. residents and 40 Australians is obtained. Consider the random variables described below: X: the number of US residents (out of 50) with blood type AB.

Y: the number of Australians (out of 40) with blood type AB.

Z: the total number of individuals (out of 90) with blood type AB.

Which of the following is true about the random variables X, Y, and Z? Check all that apply.