(1) It is not possible to allocate the attribute "Pieces" to "Order" because an order can contain many different Products, each with a different number of pieces. It can neither be allocated to "Product", because Pieces in the entity Product means the number of pieces in stock, and many orders order a product. Pieces belong to the relation between Order and Product. You can allocate the attribute Pieces to the relation (Order contains Product) or you can create a new entity called "OrderItem" (which is chosen in the next step).
(2) Create a new entity in the dictionary (OrderItem) and move it to the Master model.
(3) Create a new relation between Order and OrderItem, and another between OrderItem and Product. Update the cardinalities.
(4) The relations between Order and Products can be removed: Right Click on the relation between Order and Product; Click "Delete".
