a) List the customers (their ID).

b) List the insurance contracts (their ID) whose duration is longer then five years.

c) List the information of policies whose maximal coverage is above $10000

d) List the customers (their names) whose beneficiary in at least one of their contracts is not themselves.

1. [32 points] Express the following queries in relational algebra for the Insurance Database, consisting of the following three relations. Attempt to use as many of the different relational operators that are covered in the lecture notes, including the derived operators such as natural join. Customer: CustomerID (string) Name (string) Age (integer) Gender (one of male, female) Nationality (string, nullable) Education Level (integer, nullable) Profession (string, nullable) City (string) State (string) Address (string) Insurance Contract: ContractID (string) Start Year (integer) Stop Year (integer) Provider Code (foreign key to Policy) InsuranceType (foreign key to Policy) CustomerID (foreign key to Customer) Beneficiary (foreign key to Customer) Policy: Provider Code (string) InsuranceType (string) AnnualFee (float) MaxCoverage (float) CanDuplicate (bool) MinEducation Level (integer, the limitation to buy the insurance) Notes: If CanDuplicate is set to be False, people who bought the insurance cannot buy another insurance contract with the same InsuranceType. Otherwise, they can. Education Level is an integer. The higher the number is, the higher the level is