A small copy center uses $6570-$sheet boxes of copy paper a week. Experience suggests that usage can be well approximated by a normal distribution with a mean of $6$ boxes per week and a standard deviation of $60$ box per week. $2$ weeks are required to fill an order for letterhead stationery. Ordering cost is $$6,$ and annual holding cost is $35$ cents per box. Use Table.

a$.$ Determine the economic order quantity, assuming a $52-$week year. $($Round your answer to the nearest whole number.$)$

EOQ boxes

b$.$ If the copy center reorders when the supply on hand is $13$ boxes, compute the risk of a stockout. $($Round $"z"$ value to $2$ decimal places and final answer to $4$ decimal places.$)$

Risk