The math club surveyed 100 students about the number of math courses in which they were enrolled and the weight of their backpacks. Classify the random variables from the survey.
Number of math courses, discrete; weight of backpack, discrete
Number of math courses, discrete; weight of backpack, continuous
Number of math courses, continuous; weight of backpack, discrete
Number of math courses, continuous; weight of backpack, continuous
Unable to determine from information given