The mixing department of the Glasson Company started the month with $20000$ units in its beginning Work in Process Inventory. An additional $309000$ units were transferred into the mixing department during the month. At the end of the month $29000$ units were in ending Work in Process Inventory in the mixing department. How many units were transferred out of the mixing department during the period?

$280000$

$300000$

$318000$

$329000$