AND b. ENT c. ENND d.
Every Part has a name, and a price.
The name and price are set when the Part is created and cannot be changed. Consider another class called an Assembly. An assembly has a name, exactly 3 parts, a date, a total price and a discount percentage. The name, the discount percentage and all three parts must be specified when the assembly is created. The date of the assembly is the date it was created.