To determine the days of product inventory on hand, use the formula: Days of Inventory=Average InventoryDaily UsageDays of Inventory=Daily UsageAverage Inventory​

Given:

Average quantity on hand = 10 units

Annual sales = 60 units

Selling days in a year = 360 days

First, calculate the daily usage: Daily Usage=60 units360 days=0.1667 units/dayDaily Usage=360 days60 units​=0.1667 units/day

Then, calculate the days of inventory: Days of Inventory=10 units0.1667 units/day≈60 daysDays of Inventory=0.1667 units/day10 units​≈60 days

However, considering production days (261 days) is not relevant as the selling days (360 days) have already been used in the calculation.

Hence, the correct days of inventory based on daily usage calculation is approximately 60 days. To be more precise, using the given options: Days of Inventory=10 units(60 units/360 days)=60 daysDays of Inventory=(60 units/360 days)10 units​=60 days