In each part, indicate whether the sample should be called a self-selected sample or a convenience sample.
a. A political scientist surveys the 80 people in a class he teaches to evaluate student political views.
b. A soft drink company wants to know which of two of their drinks consumers prefer. They set up a table at a mall and people who are passing by can stop and participate in a taste test if they wish. The sample consists of those who agree to participate.