please answer bith as they are related

3. The electricity for a conventional 4 foot, 40-watt fluorescent light tube that runs every day for 8 hours costs about $12 per year. By replacing this bulb with an LED replacement tube making the same amount of light, $6 per year can be saved. The LED bulb costs $15 to purchase. Other than electricity, there are no additional operating costs for the LED tube. Assume the tube will be in place for 4 years, and to simplify the problem, assume there is no cost for fluorescent tubes (you already have plenty of them). If the discount rate is 8%, What is the benefit-cost ratio for replacing the tube? Should you replace fluorescent tubes with LEDs? 3. The electricity for a conventional 4 foot, 40-watt fluorescent light tube that runs every day for 8 hours costs about $12 per year. By replacing this bulb with an LED replacement tube making the same amount of light, $6 per year can be saved. The LED bulb costs $15 to purchase. Other than electricity, there are no additional operating costs for the LED tube. Assume the tube will be in place for 4 years, and to simplify the problem, assume there is no cost for fluorescent tubes (you already have plenty of them). If the discount rate is 8%, What is the benefit-cost ratio for replacing the tube? Should you replace fluorescent tubes with LEDs? 4. Using the same LED tube example, what is the net present value of replacing the fluorescent tube with an LED tube? Should you replace the tube using this metric