Please help solve

b. Suppose the production manager is told to reduce the safety stock of this item by 90 units. If this is done, what will the new service probability be? (Use Excel's NORMSDIST() function to find the correct probability for your computed Z-value. Round your answer to the nearest whole number.)

I'm not sure how I got this wrong. Thank you for the help!

Problem 20-22 (Algo) Annual demand for a product is 16,640 units; weekly demand is 320 units with a standard deviation of 55 units. The cost of placing an order is $160, and the time from ordering to receipt is four weeks. The annual inventory carrying cost is $0.85 per unit. a. To provide a 98 percent service probability, what must the reorder point be? (Use Excel's NORMSINV() function to find the correct critical value for the given a-level. Do not round intermediate calculations. Round "z" value to 2 decimal places and final answer to the nearest whole number.) Answer is complete and correct. Reorder point 1,506 units b. Suppose the production manager is told to reduce the safety stock of this item by 90 units. If this is done, what will the new service probability be? (Use Excel's NORMSDIST() function to find the correct probability for your computed Z-value. Round your answer to the nearest whole number.) Answer is complete but not entirely correct. Service probability 92 %