First, think about what you did to figure out the first answer when the number of kilowatt hours was 300.

C, the cost of usage, is what you found, when you used 300 as your kilowatt hours.

So, you multiplied 8.77 by 300 and added 7.57

So, C = 8.77 x + 7.57 , but this is only if the kWh or x is not more than 400

Or, the first part of your function is C = 8.77x + 7.57 if x <= 400.

Now, you need to find the part of the piecewise function when x is greater than 400:

So, for this part of the function, think about how you found $5487.77 for 700 kWh.

Think about what you did, and in place of the 700, replace it with x.

Can you figure this part out?

## Comments

Well, were you able to see how to get the other part of your function?

First, how much will the cost be with 400 kWh?

Then, how do you find the additional cost above 400 kWh?

To find the cost at 400 kWh:

C = 8.77 (400) + 7.57 = 3515.57

If you were to use 700 kWh, you would have an additional 300 kWh,

(700 - 400)

You would multiply this by the new rate of 6.574

So, for 700 kWh, the total amount would be C = (700-400)6.574 + 3515.57

So, in general, for an x amount of kWh above 400 kwh, you

would have C = (x-400)6.574 + 3515.57.

This would be the part of the function for x > 400.

So, here is your piecewise function:

8.77x + 7.57 if x <= 400

C =

6.574(x - 400) if x > 400