Let's define the monthly water bill as a function, where:
• c ,is the number of gallons consumed that month
,
• B(c), is cost of the monthly water bill
Therefore, for a consumption of 20.000 gallons or less, the monthly water bill would be:

For a consumption of more than 20.000 gallons,

Therefore:
• The cost is constant ($19.60) when the number of gallons consumed is less than or equal to 20,000 gallons
,
• The cost increases if the number of gallons consumed is greater than 20,000 gallons