I can't figure out where I am going wrong with this calculation

You have opened a margin account with $11,000 at your local brokerage firm. You instruct your broker to purchase 600 shares of Bison Corporation Stock, which currently sells for $46 per share. Three months later, the stock is selling for $50 per share. Assume interest rate is 10% a year.

You close out your position after three months. What is your percentage rate of return?

16,600 x (1+.10)^.25 = 16,600 x 1.024114 = 17,000.29

600*50 = 30,000 - 17,000.29 = 12,999.71

12,999.71 - 11,000 = 1,999.71

1,999.71/11,000 = .1818 or 18.18%