CBA 2 Financial Performance - Task 7 - Inventory holding days

This may seem like a simple question however, I can't get it!!

Task 7 on CBA 2 (AQ 2013)

Question is, work out inventory holding days for 2 scenarios, information given:

Scenario 1 Scenario 2
Sales Vol 120,000 150,000
Revenue 1,680,000 1,800,000
Gross Profit 600,000 450,000
Profit from ops 275,000 200,000
Net Assets 2,298,400 2,100,340
Inventory 147,950 167,500

I have already worked out:


Scenario 1 Scenario 2
Return on net assets 11.96 9.52
Sales price per unit 14 12
Full production cost per unit 9 9

Without COS I'm lost and I haven't got anyone else to ask so, any guidance would be appreciated!