d$)$ What is the optimal number of days in between any two orders? $8\mathrm{.}33$ days $($round your response to two decimal places$).$

e$)$ What is the annual cost of ordering and holding inventory? $ $1740\mathrm{.}14$ per year $($round your response to two decimal places$).$

f$)$ What is the total annual inventory cost, including the cost of the $5,800$ units? $ per year $($round your response to two decim