Loki query question

Hi,

I am quite new using Loki. I uses Promtail to parsing the log and send to Loki.
Here is one line of the log file after parsing through Promtail.

test=“ACL” hostname=“abc.com” elapsed_time=“123.32” ms

Not sure how to create a Loki query to get the average elapsed_time per hostname over the time(per interval)?