How can one determine the expected average shipment quantity $($i$.$e$.,$ average number of units per shipment$)$ for a transport mode analysis problem:

a$.$ Divide the total units of inventory investment by the expected number of shipments per year

b$.$ Divide the annual forecast $($in units$)$ by the expected number of shipments per year

c$.$ Divide the expected average cycle stock inventory quantity $($in units$)$ by the expected number of shipments per year