You must answer the queries using relational algebra. Answer them in any other ways, such as SQL$,$ will get a $0.$

$(1)$ Retrieve the names $($fname$,$Iname$)$ of all employees who do not work on any project.

$(2)$ Retrieve the names $($fname$,$Iname$)$ of employees who work more than $9$ hours per week on the 'ABC' project.

$("$ABC$"$ is project name.$)$

$(3)$ Retrieve the department $($dname$)$ that has a location in 'Denver'.

$(4)$ Find the names $($fname$,$Iname$)$ of employees who are directly supervised by 'Steven Miller'.