First, we are going to calculate her monthly off-peak usage:
1,185 kWh - 500 kWh = 685 kWh
Now that we know her monthly electricity consumption is 500 kWh on-peak and 685 kWh off-peak, lets calculate the cost of each plan:
Standard use plan
1,185 kWh - 600 kWh = 585 kWh
- For the first 600 KWh:
[tex]600kWh( \frac{8.5cents}{kWh} )=5100cents[/tex]
Since 100 cents = 1 dollar, [tex]5100cents( \frac{1dollar}{100cents} )[/tex] = $51
- For the remaining 585 kWh:
[tex]585 kWh( \frac{11cents}{kWh} )=6435cents[/tex]
Since 100 cents = 1 dollar, [tex]6435cents( \frac{1dollar}{100cents}) [/tex] = $64.35
Total cost of the standard use plan: $51 + $64.35 = $115.35
Interval use plan
- On-peak hours:
[tex]500kWh( \frac{16cents}{1kWh} )=8000cents[/tex]
Since 100 cents = 1 dollar, [tex]8000cents( \frac{1dollar}{100cents} )[/tex] = $80
- Off-peak hours:
[tex]685 kWh( \frac{4cents}{1kWh} )=2740cents[/tex]
Since 100 cents = 1 dollar, [tex]2740cents( \frac{1dollar}{100cents}) [/tex] = $27.40
Total cost of the interval use plan: $80 + $27.40 = $107.40
We can conclude that:
1. The new interval plan will be better for Anna since she will save $7.95 per month in her electric bill.
2. The correct answer is: b.standard use plan - $115.35; interval use plan - $107.40
