Tom uses a fixed review period inventory system in his store. He counts his inventory every 30 days and then makes an order. Ten days later his order shows up from the supplier. On one ordering occasion, he counts and finds 81 units in inventory. If the average daily demand is 10 units, the standard deviation of the (review period + lead time) demand is 17 units, and he desires a probability of not stocking out of 96%, how many units should Tom order?