Answer :
The number of boxes that are needed to be kept on hand can be found to be 7 boxes for backstock.
Since you need to keep 12 boxes on the table and you sell 7 boxes per week, you need to ensure you have enough boxes to replenish the 12 boxes on the table every 5 days.
Since you sell 7 boxes a week, you sell approximately 1 box per day (7 boxes/7 days).
Over 5 days, you would sell about 5 boxes (1 box/day * 5 days).
To maintain the 12-box inventory on the table, you would need to replace those 5 boxes during the 5-day period.
A safe approach would be to keep an additional buffer of about 2 days' worth of sales. The number of boxes needed is therefore:
= 5 boxes + 2 additional
= 7 boxes
