A hospital cafeteria manager interested in assessing the quality of the cafeteria's dinner offerings conducts a survey between 5:30 p.m. and 10:00 p.m. by asking every 20th person in the cafeteria line to rate the cafeteria's food on a rating scale ranging from 1 to 10, with 1 being inedible and 10 being delicious.

a. What type of sampling methodology what the manager using? Convenience, cluster, stratified, simple random or systematic? Explain your answer.

b. What is the most appropriate level of measurement for the rating variable: nominal, ordinal or scale?