The document contains 3 physics problems involving electricity: 1) calculating the time a light bulb drawing 4A at 12V has been on if it absorbed 14,400 joules; 2) calculating the power of an electric heater rated at 200W running at 110V; 3) calculating the electricity bill for using a 0.5A laptop plugged into 220V for 5 hours a day for 30 days at a rate of Rp 500/kWh.