Consider the following relation schemas: Department (dnumber, dname, employee_count), PK: dnumber. Employee (eid, fname, lname, salary, dno), PK: eid, FK: dno refs Department. Write triggers in PL/SQL that satisfy the following requirements: The employee_count column in the Department table records the current number of employees in each department. You should guarantee that, whenever an employee record is inserted, deleted or updated in the Employee table, the employee_count attribute always has the correct value for the affected department(s) in the Department table. Also, no department in the organization should have an average salary lower than 10,000. When the insertion, deletion or update of an employee record causes the average salary of a department to be lower than 10,000, the corresponding operation should be cancelled. You may create additional tables or views if needed. Note that your triggers will be graded based on both correctness and efficiency.