A power supply has five intermittent loads connected to it and eachload, when in operation, draws a power of 10W. Each load is inoperation only one-quarter of the time and operates independently of all other loads.
a. Find the mean value of the power required by the loads.
b. Find the variance of the power required by the loads.
c. If the power supply can provide only 40W, find the probability that it will be over loaded.