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## Homework Statement

## Homework Equations

Cost = rate x energy consumption (kWh)

Energy consumption = power (kW) x total time (hrs)

## The Attempt at a Solution

so here are my answers, can someone please verify if these are correct, thanks!

a)

To calculate power:

There are fifteen 100 W lightbulbs, so to calculate the total power, i would do the following:

P = 15 x 100 W = 1500 W = 1.5 kW

To calculate total time:

8 hrs (per day) x 365 days (since the business operates the following for one year) = 2920 hrs

To calculate electrical energy used in kWh:

E = P x t

E = (1.5 kW) x (2920 hrs)

E = 4380 kWh

To calculate total cost:

I already know the rate: 6.4 cents /kWh

cost = rate x total energy consumption (kWh)

cost = (6.4 cents /kWh) x (4380 kWh)

cost = 28032 cents = $280.32

b)

To calculate power:

P = V^2 / R

P = (120 V)^2 / 15 ohms

P = 960 Watts (multiply this by 2, since there are 2 coffee makers)

P = 960 watts x 2

P = 1920 Watts = 1.92 kW

To calculate total time:

total time = 4 hrs (since both are used for two hours each) x 365 days (since the business operates for one year)

total time = 1460 hrs

To calculate energy consumption in kWh:

Energy = power (kW) x total time (hrs)

Energy = (1.92 kW) x (1460 hrs)

Energy = 2803.2 kWh

To calculate total cost:

cost = rate x energy consumption

cost = (6.4 cents/kWh) x (2803.2 kWh)

cost = 17940.48 cents = $179.4048