Simplify this for me $"$ The production process of a plant uses a certain raw material. exogenous influences determine the usage rate of this material. to ensure continuous production, the company keeps an inventory of the raw material. a supply delay of $5$ months occurs between the ordering of additiona raw material and its arrival in the inventory. in a attempt to guard against inventory shortages, the management has decided to employ the formal policy of ordering exactly the amout of material consumed, i$.$e order rate $-$ usage rate. Assume the exogenously determined usage rate increases linearly with time $"$