The Video Store is now in 3NF

CUSTOMER (Cust_Num,

Cust_Name,

Cust_address,

Cust_phone)

VIDEO (VideoNum,

VideoName, VideoType)

RENTAL (RentalNum, Cust_Num,

Rental_date)

RENTALDETAILS (RentalNum, VideoNum,

ReturnDate, Amt_Paid)

Because, in each table every attribute depends on the primary key and not on any other key.