Jessica is selling books during the summer to earn money for college. She
 earns a commission on 
 each sale but has to pay for her own expenses.
 After a month of driving from neighborhood to neighborhood and walking
 door-to-door, she figures out that her weekly earnings are approximately a
 linear function of the number of doors she knocks on.
 She writes the equation of the function like this: E(X) = 10x - 30, where x is the
 number of doors she knocks on during the week and E(x) is her earnings for
 the week in dollars.
 Which of the following are reasonable interpretations of the y-intercept of
 Jessica's function?
 Check all that apply.
 A. She can earn $10 per week even if she does not knock on any
 doors.
 B. She will lose $10 per week if she does not knock on any doors.
 C. If she does not knock on any doors at all during the week, she will
 lose $30.
 D. Her expenses are $30 per week.