Appearing issues on Focus News Carousel

My podcast artwork is 400×400 but the Carousel isn’t the same aspect ratio. It’s wider.

Can you post a CSS revision that sets the .news-slider .carousel to 400px, and the .news-slider .carousel-list to 370px without breaking the responsive design?

I tried this:

.news-slider .carousel {
width: 400px;
}

.news-slider .carousel-list {
float: left;
width: 370px;
}

and it works great — except when displayed responsively. It breaks.

I hope you can help!

Michael