Write SQL query to solve given problem: Among the employees who are married and wish to receive e-mail promotions, how much higher is their highest pay rate from the average pay rate?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT MAX(T1.Rate) - SUM(T1.Rate) / COUNT(T1.BusinessEntityID) FROM EmployeePayHistory AS T1 INNER JOIN Person AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID INNER JOIN Employee AS T3 ON T2.BusinessEntityID = T3.BusinessEntityID WHERE T2.EmailPromotion = 2 AND T3.MaritalStatus = 'M'