posted by Jane on .
A salesman gets paid on commission, and his commission is based on how many units he sells during the month. If the salesman sells $1500 worth of units or less, he makes a flat commission of $900 plus 10% of the sale. If he sells more than $1500 worth of units, he makes an additional 6% on anything above $1500. If Mark's months earnings E were $2100 for this month, what was the total value of his sales, s?