Get details of employee working on both comp354 and comp345, Database Management System

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Consider the relations

EMPLOYEE(emp#, name)
ASSIGNED_TO(project#, emp#)
PROJECT(project#, project_name, chief)
Express the subsequent queries in Relational Algebra

(i) Get details of employee working on both comp354 and comp345 project numbers.
(ii)Find out the employee number of employee who do not work on project comp678

(i) EMPLOYEE (ASSIGNED TO ÷∏project # (σ(project#='comp351' ∨ project#='comp 345 ASSIGNED _TO)))
(ii) ∏Emp#(EMPLOYEE)-∏Emp# (project#='c 678' ASSIGNED_TO))

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