A salesperson succeeded in finding a buyer for a tract of land that is 250' x 350'. It sold at $300 per front foot, and the commission was 6%. If the listing broker gave the selling brokerage 45% and the selling broker gave the salesperson 50%, how much commission did the listing broker keep?
a) $7,875
b) $9,000
c) $10,125
d) $11,250