Consider a database schema with four relations: SUPPLIER, PRODUCT, CUSTOMER, and CONTRACTS. Both the SUPPLIER and the CUSTOMER relations have the attributes Id, Name, and Address. An Id is a nine-digit number. PRODUCT has PartNumber (an integer between 1 and 999999) and Name. Each tuple in the CONTRACTS relation corresponds to a contract between a supplier and a customer for a specific product in a certain quantity for a given price. a. Use SQL DDL to specify the schema of these relations, including the appropriate integrity constraints (primary, candidate, and foreign key) and SQL domains. b. Specify the following constraint as an SQL assertion: there must be more contracts than suppliers