I beg your help on this excercice. Thank you.

The number of hours spent studying by students the week before exams is normal distributed with standard deviation 8.4 hours. A random samole is taken to estimate the population mean number of hours studying.

A) How large a sample is needed to ensure that the probability tha the sample mean differs from the population mean by more than 2 hours is less than 0.05?

B) without doing calculations, state whether a larger or smaller sample than in part A) would be required to guarantee that the probability of the sample mean differs from the population mean by more than 2 hours is less than 0.10.

C) without doing calculations, state whether a larger or smaller sample than in part A) would be required to guarantee that the probability of the sample mean differs from the population mean by more than 1.5 hours is less than 0.05.

Thank you.