Alt Investement Mock Exam

Hi guys, I’m struggling one question in the CFAI MOCK 2011 in the Morning session : Q - 113 : how do funds calculate their NAVs? (I’m not sure to be able to post the entire question because of the copyright) I don’t understand why only closed-end mutual fund calculate their NAV as follows : Assets - Liabilities / Number of shares Outstanding. Thank you by advance for your help…