6.92 Resistors being used in the construction of an aircraft guidance system have lifelengths that follow a Weibull distribution with  2 and  10

(measurements in thousands of hours).

a Find the probability that a randomly selected resistor of this type has a life length that exceeds 5,000 hours.

b If three resistors of this type are operating independently, find the probability that exactly one of the three resistors burns out prior to 5,000 hours of use.
c Find the mean and variance of the life length of such a resistor.