Create a one-to-many (1:M) relationship between Salesperson and Customer

Create a bridge entity between Order and Product and name it ProductOrder 

The primary keys of Order and Product together become composite key for the bridge entity named ProductOrder

Create a many-to-many (M:N) relationship between Customer and Order

Create a one-to-many (1:M) relationship between Customer and Order

Add the primary key of Customer as a foreign key in Salesperson 

Identify other additional attributes and add them to their corresponding entities as necessary to complete the ERD

Add the primary key of Customer as a foreign key in Order

Add the primary key of Salesperson as a foreign key in Customer

Create one-to-many (1:M) relationships linking Product and Order to the bridge entity ProductOrder 

Create one-to-many (1:M) relationships linking Customer and Order to the bridge entity CustomerOrder 

Add the primary key of Order as a foreign key in Customer 

Add the primary key of Order as a foreign key in Product

Add the primary keys of Customer and Order as foreign keys in the bridge entity named CustomerOrder 

Create a bridge entity between Customer and Order and name it CustomerOrder

The primary keys of Customer and Order together become composite key for the bridge entity named CustomerOrder

Add the primary keys of Order and Product as foreign keys in the bridge entity named ProductOrder

Create the entities Salesperson, Customer, Order and Product

Create a one-to-one (1:1) relationship between Salesperson and Customer