How to show the total number of employees in this database design?

I have the following database design:

Employee Table: EmployeeID, Name, OrgCode
Department Table: OrgCode, DepartName
CompleteSurvey Table: ID, RespondantID, QuestionsAnswersID
Questions Table: QuestionID, Question
Answers Table: AnswerID, Answer
QuestionsAnswers Table: ID, QuestionID, AnswerID

I wrote a query that shows each question with all possible answers and the total number of participants in each question even if there is one of the possible answers without any participant. This results will be shown in each department.

What I have to do now is to modify this query to show the total number of employees in each department besides the total number of participants that I already got, then show the participation percentage which is the total number of participants/ total number of employees.

So how to do that?

The query:

SELECT     
   TOP (100) PERCENT 
   COUNT(DISTINCT CompleteSurvey.RespondantID) AS [Total Number of Participants], 
   dbo.Answers.Answer, dbo.Questions.Question, 
   dbo.Departments.DepartmentName
FROM
   dbo.Questions 
INNER JOIN
   dbo.QuestionsAnswers 
   ON dbo.Questions.QuestionID = dbo.QuestionsAnswers.QuestionID 
INNER JOIN
   dbo.Answers ON dbo.QuestionsAnswers.AnswerID = dbo.Answers.AnswerID 
CROSS JOIN
   dbo.Departments 
LEFT OUTER JOIN
   (SELECT     
        dbo.Employees.OrgCode, CompleteSurvey_1.QuestionsAnswersID, 
        CompleteSurvey_1.RespondantID
    FROM          
        dbo.CompleteSurvey AS CompleteSurvey_1 
    INNER JOIN
        dbo.Employees 
        ON dbo.Employees.EmployeeID = CompleteSurvey_1.RespondantID) AS CompleteSurvey 
        ON dbo.QuestionsAnswers.ID = CompleteSurvey.QuestionsAnswersID 
               AND dbo.Departments.OrgCode = CompleteSurvey.OrgCode
GROUP BY 
    dbo.Answers.Answer, dbo.Questions.Question, dbo.Departments.DepartmentName
ORDER BY 
    dbo.Questions.Question, dbo.Answers.Answer, dbo.Departments.DepartmentName