Savannah is choosing between two cell phone plans. Plan A charges $60 a month
plus a one-time activation fee of $75. Plan B charges $63 a month plus a one-time activation fee of $15. Evaluate the
expressions 60m + 75 and 63m + 15 when m = 18 to find the total cost for each cell phone plan for 18 months. What is the difference in cost between the two cell phone plans?