Which of the following situations describes a linear relationship?
a. during the hour before closing time, the number of customers at a coffee shop decreases by one-fifth every ten minutes.
b. the total cost of a taxi fare increases by $0.50 for each mile driven.
c. each month, the amount of an unpaid parking ticket doubles.
d. the annual amount of car insurance decreases by 5% for every year of having a good driving record.