and transformers, all using a certain type of copper wire. The firm's demand for this wire is approximately normal, averaging $20$ spools per week, with a standard deviation of $6$ spools per week. Cost per spool is $$24$; ordering costs are $$25$ per order; inventory handling cost is $$4\mathrm{.}00$ per spool per year. Acquisition lead time is four weeks. The company works $50,5-$day weeks per year. $(2$ points$)$

a$.$ What is the optimal size of an order, if minimization of inventory system cost is the objective?

b$.$ What are the safety stock and reorder point if the desired service level is $90\%?$