How to apply SOLID design principles and design patterns on the class diagram and sequence diagram?

How to apply SOLID design principles and design patterns on the class diagram and sequence diagram of this case study!

Case Study:

The government procurement system can provide bidding procurement for many types of products.    
The purchasers could publish the purchase information, which specifies the product type.    
The suppliers could subscribe to certain product types of purchase demand. 
Once a new purchase demand is released for that product type, the suppliers can immediately receive the purchase demand.    
According to different qualifications, suppliers are divided into senior suppliers and ordinary suppliers.     
Only senior suppliers can view orders of wholesale. The ordinary suppliers may become senior suppliers in the future and vice versa.    
The suppliers can quote for the purchase order.     
The supplier offering the lowest price can get the order.    
The system may add new product types in the future. The suppliers can subscribe to or cancel a certain type of product purchase demand at any time.