Question

Suppose a baker claims that the mean time to prepare a cake is at most 360 minutes. A sample of 25 bakers in randomly selected and it is found that the mean time taken by them to prepare a cake was 270 minutes. Assume also that standard deviation is known to be 120 minutes. Assuming the time to prepare a cake is normally distributed and using a 0.05 level of significance, would you conclude the baker’s claim is true?