Weekly demand for cereal boxes at a retailer is normally distributed with a mean of 900 boxes and a standard deviation of 150. Currently, the store places orders to the supplier, with a reorder point of 3,900 boxes. The order quantity to the supplier is fixed at 4,000 boxes. Replenishment lead time is 4 weeks, fixed order cost per order is $200, each box costs the retailer $10, and the inventory holding cost is 20% per year. With a safety stock of 350 boxes, what is the approximate service level (round to two decimals)?