Consider a retailers inventory problem over multiple time periods. Assume the per-unit holding cost is $10 and the per-unit backlogging cost is $30. Demand in every time period is normally distributed with mean 100 and standard deviation 10. The beginning inventory of period 1 is equal to 100. Assume that at the end of every period, 10% of the leftover inventory (if any) gets expired and discarded. Assume every order placed at the end of each period will arrive at the beginning of the next period.

a) Describe the optimal ordering policy (that minimizes the total holding and backlogging costs) in details.

b) Build the Excel simulation to quantify the average costs under the optimalordering policy. (attach a picture of the excel)