1. Relational Algebra Use the following relational database schema to answer the queries using relational algebra. You may NOT use Cartesian products. Professor SSN ProfName Salary Nationality Teaches Prof SSN Crs Code Semester Coursel Crs Name Code Credit Hours . Each of the attribute is explained as follows: SSN: the unique ID of a professor ProfName: the name of a professor Nationality: the nationality of a professor (ie, Emirat...) Semester when the course taught (t.e. Summer...) CrsNamethe name of a course Code: the unique ID of a course Credit_Hours: the number of credit hours of a course. 1). Find the name of professors who taught the course "IS340" but never taught the course "IS210