How much cash would you need to purchases 500 shares of stock at $21 per share plus brokerage commissions of $125, if you purchase on margin and the margin requirement is 50%? $10,625 $5,312,50 $10,500 $5,250 people with seats on the NYSE who execute stock trades for others are called day traders. floor traders. stock traders. commission traders. Fees charged by brokerage firms are set by the NYSE are set by the Federal Reserve are set by the National Association of Securities Dealers vary according to the services offered