That's an excellent question but we don't have enough information to answer it. We would need to know how the electrical energy is generated. Nuclear, hydroelectric, coal burning, wind, and natural gas burning all produce different amounts of carbon for the same amount of electrical energy. If the utility that supplies your house uses nuclear or wind, then you can leave both bulbs shining 24/7 and they're not responsible for any carbon.
The probability it will take 20 minutes or more is about 6.3%.
Answer: b.
Step-by-step explanation: