For the basic charge (starting value), it is charge at t = 0.
Therefore, the basic charge is $15.67.
Next, let's determine the unit rate charge.
Let,
x₁, y₁ = 0, 15.67
x₂, y₂ = 5.0, 19.98
We get,
Therefore, the unit rate change is $0.862.
The answer is, therefore, letter C : $15.67, $0.862 per therm