In order to quote a price to sell the remaining 360 units, we will have to understand that fixed selling expenses and fixed administrative expenses have already been covered by usual sales of 30390, Thus in order to produce the 360 units the organisation will incur variable expenses per unit, thus they can quote a price which is lower than what they quote normally.
In the given question the incremental selling and administrative cost will be as below:
Sales Commissions $2.6
Variable Administrative Expenses $2.10