Identify the type of sampling technique used in the following studies:

a. A telephone surveyor calls people listed in the phone book in alphabetical order. The survey is administered to the first 100 African American men and 100 African American women who agree to participate.

b. A pest control company uses a random number generator to select 100 current customers from its customer database to survey regarding their satisfaction with the firm’s services.

c. The state of Texas randomly selects 10 school districts in the state, then randomly selects 5 middle schools within each district to participate in a survey.