After extensive data analysis it has been determined that the weekly demand for a certain product of a given company is normally distributed with a mean 100 and standard deviation of 20.

1. what is the probability that weekly demand is within 25% of its average value?
2. If the firm can only replenish its supply at the start of the week, what is the smallest amount of inventory that the company can have on hand at the start of the weekend be sure it will have sufficient stock to meet demand 80% of the time?