Write the following queries in relational algebra, using the university schema.

classroom$($building$,$room$\_$number, capacity$)$

department$($dept$\_$name, building, budget$)$

course$($course$\_$id$,$title$,$ dept$\_$name, credits$)$

instructor$($ID$,$name$,$ dept$\_$name, salary$)$

section$($course$\_$id$,$sec$\_$id$,$semester$,$ year, building, room$\_$number, time$\_$slot$\_$id$)$

teaches $($ID$,$course$\_$id$,$sec$\_$id$,$semester$,$ year$)$

student$($ID$,$name$,$ dept$\_$name, tot$\_$cred$)$

takes$($ID$,$course$\_$id$,$sec$\_$id$,$semester$,$ year, grade$)$

advisor $($s$\_$ID$,$i$\_$ID$)$

time$\_$slot$($time$\_$slot$\_$id$,$day$,$ start$\_$time, end$\_$time$)$

prereq$($course$\_$id$,$prereq$\_$id$)$Find the ID and name of each instructor in the Physics department.

Find the ID and name of each instructor in a department located in the building $$Watson$.$

Find the ID and name of each student who has taken at least one course in the $$Comp$.$ Sci.$$ department.

Find the ID and name of each student who has taken at least one course section in the year $2018.$

Find the ID and name of each student who has not taken any course section in the year $2018.$