Question 4 (35%) EXCEL Spreadsheet Simulation Refer to Example '(s, S) policy inventory system' simulation in the lecture note (3. Simulate and analyze an inventory system for 25 periods (i = 0, ..., 25) to decide how many items it should have in inventory every day. Assume that there are daily demands and the inventory is reviewed every days. New order is placed following (a,5) policy. General parameters are given in Figure 1. The random variables are given in Figure 2. Solution sheet example is represented at Figure 3. (a) Make an EXCEL simulation sheet refer to Figure 3 (b) Calculate an average total cost and a standard deviation for an entire periods (c) Repeat your simulation 10 times with different (s, S) according to your own intuition and draw a plot: trial index va. average cost for each trial. Figure out the best (a,5) across your trials