Question

Part 1 of 2
The monthly water bill is a function of the number of gallons used. The cost is $9.20 for 10,000 gal or less. Over 10,000 gal, the cost is $9.20 plus $1 for each 1000
gal over 10,000 with any fraction of 1000 gal charged at a fraction of $1. On what interval is the cost constant? On what interval is the cost increasing?
On what interval is the cost constant? Select the correct choice below and, if necessary, fill in the answer box to complete your choice.
O A. The cost is constant on the interval(s).
(Type your answer in interval notation. Use a comma to separate answers as needed.)
OB. The cost is never constant.

Answer 1

The cost is constant for the interval $[0,1000]$.

The cost is never constant for the interval $(10,000, \infty)$.

The cost for $10,000$ gal or less is $$9.20$.

So, the cost is constant from $0$ gal to $10,000$ gal.

Therefore, the cost is constant for the interval $[0,1000]$.

The cost for over $10,000$ gal is $$9.20 +$ $$1$ for each $1000$ over $10,000$.

For example: The cost for $11,000$ gal is $$10.20$.

The cost for $12,000$ gal is $$11.20$.

So, the cost is never constant above $10,000$ gal.

Therefore, the cost is never constant for the interval $(10,000, \infty)$.

Learn more about open intervals here:

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