Flint Corp. makes and sells deck coating which is sold by the gallon. Two pounds of sand are needed to make one gallon of deck coating. Budgeted production of deck coating for the next two months follows:

$\backslash$table$[[$September$,21,700$ gallons$],[$October$,34,200$ gallons$]]$

The company wants to maintain monthly ending inventories of sand equal to $20\%$ of the following month's production needs. On August $31,8,680$ pounds of sand were on hand.

How much sand should be purchased in September?

Sand to be purchased