Summarize data within Spreadsheet

Hello,

I am looking for a way to summarize the data presented on this spreadsheet, usually this spreadsheet has 90,000 rows, but I have trimmed it down.

For each serial number on the "Raw" sheet there is a meter read for each day of the month. What I wish to find do is pick only the first read of each month and then the last read of each month for each serial number and calculate the volume for columns D and E.

I have tried a pivot table but get so far and get stumped.

Any help or suggestions how to tackle this would be welcomed!!
I have found a work around but 2 hours later, this is not a practically solution month over month!!
Thanks