I need some help with these questions please, and would you show how you got the answer to them so I can learn how to do what you did

2 Variable Lead Time One of the world's largest steel producers receives steel plates from Asia with lead times ranging from 10 to 14 weeks (two standard deviations from the mean). The new operations manager has been falling short on service, and is searching for the cause. The main reason under consideration is the safety stock calculation that currently considers a fixed lead time equal to the mean. This seemed logical to the last operations manager as the variance (and subsequent standard deviation) was so small, they chose to ignore it and rely on the mean only. With the weekly demand for steel plates following the distribution DN(9000,6250000), they are in need of assistance to determine a systematic safety stock policy to adhere to their 99% service level. 8. What is the distribution of lead time? (Hint: just look at the first sentence of the scenario and consider the symmetry of the bell curve.) 9. It was stated that the operations manager ignored the variability of the lead time in the safety-stock calculation. Under this policy, what was the derived safety stock? 10. Taking into consideration the variable lead time, what is the correct safety stock