Please provide the response in excel file.

Home Depot sells the LawnBoy T650 lawn mowers at 49 stores in the Pacific Northwest. Weekly demand for the T650 at each of the stores is identical and given by:
X ~ Normal (50, 30)
Assume that the demands at the 49 stores are independent of each other. The manufacturer’s lead time for supplying the mowers is 9 weeks. Home Depot has a stated policy of 90% cycle service level for mowers. 
a. How much safety stock is required at each store?
b. The chain is considering centralizing the inventory of the T650 to a distribution center that will serve all 49 stores. How much safety stock would be required at the DC to provide the same cycle service level of 90%?
c. If the cost of each mower is $400, and Home Depot uses a 30% holding cost rate, what is the annual savings for the chain in inventory holding costs as a result of the centralization?