Thomas Company has budgeted sales in units for the next five months as follows:

$\backslash$table$[[$June$,8,400$ units$],[$July$,7,200$ units$],[$August$,7,300$ units$],[$September$,6,400$ units$],[$October$,5,100$ units$]]$

Past experience has shown that the ending inventory for each month should be equal to $20\%$ of the next month's sales in units. The inventory on May $31$ contained $1,680$ units. The company needs to prepare a production budget for the next five months.

The total number of units produced in September should be: