For the employees who have the highest pay frequency, please list their vacation hours.
highest pay frequency refers to PayFrequency = 2
SELECT T2.VacationHours FROM EmployeePayHistory AS T1 INNER JOIN Employee AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID WHERE T2.BusinessEntityID = ( SELECT BusinessEntityID FROM EmployeePayHistory ORDER BY Rate DESC LIMIT 1 )