I need an algorithm based on sales

i need an algorithm that tells me based on my sales what i should be ordering.



Onhand means what is with the retailer - Available or in store or damaged

Rserverd - reserved for sale and cnanot be sold further

Available - availabel to sell right away

PO- purchase orders for that item currently

qty - PO Qty for that item

Jan - for now it is yday sale qty

Monthly average - yes month avg sales

month of supply - how many months of supply do we have now