Consider the following information about travelers on vacation. There are 20 people check work email, 30 people use a cell phone to stay connected to work, 18 people bring a laptop with them.
Select randomly 2 people. Let X be the number of people using a cell phone in 2 people who are
selected. Find pmf of X and mean of X.

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.