Write SQL query to solve given problem: What is the current payrate of Rob Walters? Calculate the percentage increment from his previous payrate.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.Rate , (MAX(T2.Rate) - MIN(T2.Rate)) * 100 / MAX(T2.Rate) FROM Person AS T1 INNER JOIN EmployeePayHistory AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID WHERE T1.FirstName = 'Rob' AND T1.LastName = 'Walters'