Kwikset has 300 shares in the stock. He sold it for 12.34 dollars per share:
So:
=> 300 12.43 dollars = 3702 dollars is the total money that she get after selling the stocks.
Now, it will be deducted by 5.8% commission.
=> 3702 .058 = 214.716
=> 3702 - 214.716 = 3487.284 dollars
or -3487.28 dollars.