I have a part that I need to create, but when making the sketch to create the part, it won't allow me to extrude the part because there are open contours. My professor has told me to simply redraw the sketch and trim entities. I've tried to redraw it several times, but it still won't allow me to close the contours. I know that there are open contours; you can see them if you zoom in really close. But I can't figure out how to close them to make the part. Could anyone help me with this issue?

Here's the drawing that I need to replicate. http://i.imgur.com/NJdPMA5.jpg