$($i$)$ Figure $1$ shows an example relational database about employees working on projects:

$($ii$)$ Construct an SQL statement for the following query: $$List the name of the project, the number of employees working on the project, and the total employee cost $($HourRate $*$ TotalHours$)$ on the project for those projects that have involved employees$.$ What would be the result table that the SQL statement produces?

$($iii$)$ Describe the following queries using the Relational Algebra:

a$.$ List the names of the projects with no employees working on them;

b$.$ List pairs of names for employees working on the same projects.

$($iv$)$ This part of the question is about referential integrity constraint.

a$.$ If the DBA wants to enforce the referential integrity constraint on the existing tables in

b$.$ If the enforcement action is NO ACTION, what would happen if there is an attempt to remove the row about BlueSea project from the Projects table?

c$.$ If the employees are permanent where they work on different projects from time to time, what would be the most sensible enforcement action to take when a specific project record is removed? If the employees are only contracted to work on specific projects, what would be the most sensible enforcement action to take when the specific project records are removed? Justify your answer.