$(25$ points$)$

A decision maker wants to find an order plan for the next $8$ months using Silver$-$Meal Heuristic method. Through the application of the method, he obtains average per period costs $($AC$)$ which are shown in the following graphic. Note that, the first iteration starts in month $1,$ continued in month $2$ since average perperiod cost is less than the previous one $)<mi\; id="EditorElement\_708086">(</mi><mn\; id="EditorElement\_708078">8</mn><mn\; id="EditorElement\_708079">0</mn>$ and ends in month $3$ when average per$-$period cost exceeds the previous one Then, the second iteration starts from month $3.$ Likewise, the second iteration is stopped in month $6$ and the third iteration starts from month $6$ and stopped in month $8.$ Let inventory holding cost be $$1$ per unit per month. First month's demand is $60$ units. Assume there is no inventory at the beginning of month $1.$

a$)$Find monthly demands.

b$)$ Using the related data from the graphic, find the resulting order policy of Silver$-$Meal Heuristic $($when to order and how much to order$).$