6.d.    A Laboratory has several chemists who work on one or more projects. Chemists also may use certain kinds of equipment on each project. Attributes of CHEMIST include Employee_ID (Identifier), Name and PhoneNo. Attributes of PROJECT include Project_ID (Identifier), and Start_Date. Attributes of EQUIPMENT include Serial_No and Cost. The organization wishes to record Assign_Date, that is, the date when a given piece of equipment was assigned to a particular chemist on a particular project. A chemist must be assigned to at least one project and one equipment item. A given piece of equipment need not be assigned, and a given project need not be assigned either a chemist or equipment item.