The management of some industry is considering a new method of assembling its products. The present method requires 41.3 minutes, on average, to assemble one unit. The mean assembly time for a random sample of 16 units using the new method is 40 minutes and the sample standard deviation is 5 minutes. Assuming that the assembly time of all products is normally distributed, what is the critical value used to test the claim that the new method is better than the present at a 1% significance level? *