A survey of families living in a certain city was conducted to collect information on the following variables: age of the oldest person in the family, number of family members, number of males in the family, number of females in the family, whether or not they own a house, income of the family, whether or not the family took vacations during the past one year, whether or not they are happy with their financial situation, and the amount of their monthly mortgage or rent.

a. Which of these variables are qualitative variables?
b. Which of these variables are quantitative variables?
c. Which of the quantitative variables of part b are discrete variables?
d. Which of the quantitative variables of part b are continuous variables?