A phone company charges for service according to the formula: C(n) =65 + 0.25n, where n is the number of minutes talked, and C(n) is the monthly charge, in dollars.

1. What is the fixed charge, even if you do not talk on your phone?
2. How much are you charged for each minute of talk time (Rate of Change in total charges)?
3. If there is an alternative plan that charges C(n) = 75 + .05 , which plan would you accept if you talk at least 400 minutes per month?
4. How many minutes of talk time will make you indifferent between the two plans?