Joanne is charged a base rate of $40.00 each month for her cell service. She upgrades her phone and chooses to make 18 monthly payments of $25 to pay for her new Samsung. She must also pay 25 cents for each text that she sends. Which function represents Joanne's phone charges each month for the next 18 months?
A) y = .25x + 65
B) y = .25x + 40
C) y = .25x + 72
D) y = 25x + 40