A$)$ Consider the relational database described below, primary keys are underlined $(25$ points$)$

Student $($snum: integer, sname: string, major: string, level: string, age: integer$)$

Class $($name: string, meets at: string, room: string, fid: integer$)$

Enrolled $($snum: integer, cname: string$)$

Faculty $($fid: integer, fname: string, deptid: integer$)$

Consider following database instances:

Student

$\backslash$table$[[$snum$,$sname,major,level,age$],[101,$Helen,CS$,$JR$,19],[102,$Charles,CS$,$SR$,21],[103,$Andy,CS$,$GR$,25],[104,$Bob,CS$,$SR$,23],[105,$Zorba,CS$,$GR$,31]]$

$\backslash$table$[[$Enrolled$],[$snul$,$cname$],[101,$CSC$343],[101,$CSC$443],[101,$ECE$300],[102,$CSC$343],[102,$ECE $201],[103,$CSC$343],[103,$CSC$443],[103,$ECE$300]]$

Class

$\backslash$table$[[$name$,$meets$\_$at$,$room,fid$],[$CSC$343,$W$1,$BA$1180,201],[$CSC$443,$T$2,$BA$1170,202],[$ECE$300,$M$1,$BA$1180,203],[$ECE$201,$F$12,$BA$1190,203],[$CSC$165,$R$3,$BA$1170,203]]$

Faculty

$\backslash$table$[[$fid$,$fname,deptid$],[201,$S$.$ Jackson,$301]]$

Write the following queries in SQL$.$ No duplicates should be printed in any of the answers.

Find the names of all Juniors $($level $=JR)$ who are enrolled in a class taught by I. Teach.

For each level, print the level and the average age of students for that level.

For all levels except JR$,$ print the level and the average age of students for that level.

Find the names of students enrolled in the maximum number of classes.

Find the names of faculty members for whom the combined enrollment of the courses that they teach is less than five.