At the beginning of the year, Cullumber had beginning inventory of $1680$ scooters. Cullumber estimates it will sell $4200$ units during the first quarter of the current year, with a $10\%$ increase in sales each quarter. It is Cullumber's policy to maintain an ending inventory equal to $20\%$ of the next quarter's budgeted sales. Each scooter costs $$84$ to produce and sold for $$126.$ How much is the budgeted sales revenue for the third quarter of the current year?

$$ $$640332.$