Jane takes her cat to the veterinarian. The veterinarian charges a $45 initial charge for the visit plus $22.50 per vaccine. Which equation can be used to find y, the total cost of the appointment, if x represents the number of vaccines?

A. y = 45x + 22.5
B. x = 22.5 y + 45
C. y = 22.5(x + 45)
D. y = 22.5x + 45