Answer:
The total cost C = $10 + $0.05·x
Explanation:
The given parameters are
The cost of the cell phone plan per month = $20
The number of minutes of free calls that one can make in a month = 200 minutes
The cost of additional minutes of cell phone call = 5 cent
5 cents to a dollar = $0.05
The total number of minutes of calls made in a month = x
The time duration of a person's usage of the cell phone in a month > 200 minutes
The total cost C of a person's usage per month is given by;
C = $20 + $0.05 × (x - 200) = $20 + 0.05·x - $10
C = $10 + $0.05·x
Where x > 200.