Write SQL query to solve given problem: Between 1/1/2017 and 4/1/2017, what is the average server time of calls under the server DARMON?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT AVG(CAST(SUBSTR(ser_time, 4, 2) AS REAL)) FROM callcenterlogs WHERE `Date received` BETWEEN '2017-01-01' AND '2017-04-01'