The following function gives the total cost of a water bill dependent on the amount of time (t) in hours that the water runs.
C(t) = 4(0.21)^t
This function is an exponential function where the cost (C) varies with time (t).
The cost of the water bill is given by the equation C(t) = 4(0.21)^t.
In this equation, 0.21 is the rate of decrease of the cost over time, and t represents the number of hours that the water runs.
To calculate the total cost of the water bill for a given value of t, you can substitute the value of t into the equation and evaluate it.
For example, if the water runs for 3 hours, you would substitute t = 3 into the equation:
C(3) = 4(0.21)^3
C(3) = 4(0.009261)
C(3) ≈ 0.037058
Therefore, the total cost of the water bill for 3 hours of running water would be approximately $0.037058.