(b) A manufacturer of a certain electronic tube claims that the average life span of tubes will exceed 1000 hours from the past experience the standard deviation is known to be 120 hours. A retailer is willing to order for a large consignment at the manufacturer claim is true. The retailer sets a sample of 36 tubes tested and finds that the sample mean lifespan is 1040 hours. Should the retailer order for the consignment? Assume the sample is taken from a normal distribution and alpha = 5% significance level [6 marks]