Q3 llkV SF6 circuit breakers in electrical distribution substations in an industrial park must be periodically maintained to prevent unexpected faults. An engineer claims that on average, the circuit breakers will fail less than 10 months after the last maintenance work due to the surrounding atmospheric conditions. Based on his claim, he suggests to reduce preventive maintenance cycle time. From a sample of 30 circuit breakers, the mean operating hours before circuit breaker failure is 6845 hours with a standard deviation of 766 hours. Let X is the average operating hours before fail and 01:0.05. Assume 30 days per month in the calculation. (a) Write the null hypothesis, alternative hypothesis and claim for X. (5 marks) (b) Determine the test types and data. (6 marks) (c) Calculate the critical value and the test statistics. (5 marks) (d) Evaluate the decision using the graph. (6 marks) (e) Conclude the hypothesis test for X