Margaret is economizing by turning off her space heater and warming herself with a toaster. She pushes the toaster plunger down and dozes off, but after 4 min it pops up again. Eventually the cold wakes her up, so she pushes the plunger down again and gets a little more sleep. This happens once every 15 min, with the toaster engaged for 4 min each time. It is a poor night’s sleep, but she is determined to save money. Energy costs 9 cents per kilowatt-hour, and a 120-V source is used.

(a) How much does it cost to operate an electric toaster for 4 min if its resistance is 11.0 Ω?

(b) How much would it cost to operate a 5.0-Ω-heater connected across 120 V for 8 h?