A home has fifteen 100 W light bulbs. During Energy Conservation week, these are replaced with 20W LED light bulbs. If these lights are on 12 hours per day, seven days per week, and the cost of electricity is $0.24 per KWH, what is the annual savings

Awall of 0.5m thickness is to be constructed from a material which has average thermal conductivity of 1.4 w/mk. the wall is to be insulated with a material having an average thermal conductivity of 0.35 w/mk so that heat loss per square meter shall not exceed 1450 w. assume inner wall surface temperature of 1200°c and outer surface temperature of the insulation to be 15°c. calculate the thickness of insulation required.