[Twenty Fourteen] Featured Image Max Width

Hello,

I am using a child-theme of Twenty Fourteen and when I set the featured image, the max-width is only limited to 672px. Therefore, there’s an awkward blank space beside the featured image as shown in the screenshot below:

So my question is that, is there a way to change the max-width to allow the featured image to cover the entire section?

P.S. The image I uploaded was 1280px if anyone wondered.