# Chapter 28 - Fundamentals of Circuits - Exercises and Problems - Page 792: 40

(a) $\$14.40$(b) It would take 34.7 months to recover the additional cost. #### Work Step by Step (a) We can find the cost of electricity for 30 days:$C_e = (\$0.10/kWh)(1.0~kW)(30\times 24~h)(0.20) = \$14.40$(b) We can find the cost of electricity for 30 days for the more expensive refrigerator:$C_e = (\$0.10/kWh)(0.80~kW)(30\times 24~h)(0.20) = \$11.52$We can save$\$2.88$ each month. We can find the number of months it takes to recover the additional cost: $\frac{\$100}{\$2.88} = 34.7$ It would take 34.7 months to recover the additional cost.

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