Tanya earns $13.50 per hour at her part-time job. When she works z hours, she
 earns 13.50z dollars. Which of the following expressions gives the amount, in dollars,
 Tanya will earn if she works 3z hours?
 A. 3z+13.50
 B. 3(13.50z)
 C. 13.50(z+3)
 D. 3+13.50z