What are the first names, office locations of all lecturers who have taught some course?
select t2.emp_fname, t4.prof_office, t3.crs_description from class as t1 join employee as t2 on t1.prof_num = t2.emp_num join course as t3 on t1.crs_code = t3.crs_code join professor as t4 on t2.emp_num = t4.emp_num