Question

1. office services as shown in example 3 on page 55, many public utilities charge customers according to a tier or block system in order to encourage conservation. for example, a certain electric utility divides a customers usage of kilowatt - hours (kwh) into five tiers according to the following table:

tier	usage	cost per kwh
2	next 60 kwh	$0.05610
3	next 140 kwh	$0.16409
4	next 200 kwh	$0.21260
5	remaining kwh	$0.26111

use this table to calculate the cost of using (a) 350 kwh and (b) 525 kwh. (round to the nearest cent.)

Explanation:

Step1: Calculate cost for 350 kWh

For the first 200 kWh, cost = $200\times0.02930 = 5.86$.
For the next 60 kWh, cost = $60\times0.05610= 3.366$.
The remaining usage is $350 - 200 - 60=90$ kWh. For these 90 kWh, cost = $90\times0.16400 = 14.76$.
Total cost = $5.86+3.366 + 14.76=23.986\approx23.99$.

Step2: Calculate cost for 525 kWh

For the first 200 kWh, cost = $200\times0.02930 = 5.86$.
For the next 60 kWh, cost = $60\times0.05610 = 3.366$.
For the next 140 kWh, cost = $140\times0.16400=22.96$.
For the next 200 kWh, cost = $200\times0.21260 = 42.52$.
The remaining usage is $525-(200 + 60+140 + 200)=25$ kWh. For these 25 kWh, cost = $25\times0.26111 = 6.52775$.
Total cost = $5.86+3.366+22.96+42.52+6.52775 = 81.23375\approx81.23$.

Answer:

(a) $23.99
(b) $81.23