The cost of energy delivered to residences by electrical transmission varies from $0.070/kwh to $0.258/kwh throughout the united states; $0.110/kwh is the average value. (a) at this average price, calculate the cost of leaving a 40-w porch light on for two weeks while you are on vacation? (b) at this average price, calculate the cost of making a piece of dark toast in 3.00 min with a 925-w toaster?