A monthly demand for a new product is normally distributed with a mean of 2000 and a standard deviation of 200. For a given month, find the probability that the demand is :

1. more than 2350
2. less than 1600
3. between 1600 and 2350

When an order is placed ,one month is required for the delivery . If the probability that the stock will run out is set to be less than 0.01,

4.calculate the amount of stock to order at the beginning of the month