what are n, x, and p? [About 39% of students participate in a community volunteer program outside of school. If 42 students are selected at random, find the number of students expected to participate.]
a) n = sample size, x = number of students participating, p = probability of students participating
b) n = population size, x = number of students participating, p = probability of students participating
c) n = sample size, x = sample mean, p = population mean
d) n = population size, x = sample mean, p = population mean