Consider the following relational schema where eid and did are keys for their relations:

Emp(eid:integer, ename:string, age:integer, salary:real)

Works(eid:integer, did:integer, pc time:integer)

Dept(did:integer, dname:string, budget:real, managerid:integer)

Write a SQL query that:

(a) Print the names of every employee who works in Hardware, Software, and Research departments.

(b) Return the names of every department without any employee.

(c) Print the managerids of managers who manage only departments with budgets greater than $1.5 million.

(d) Print the name of employees whose salary is less than or equal to the salary of every employee.