change size image category and sub category

good morning, looked everywhere but can not find the solution to my question.
I want to resize the images that are displayed in categories and subcategories of my products.

I want pictures of categories and subcategories are displayed at a size of 400×150 and not as small as they are now.

Can you help me with this issue?

PD: Sorry for my English
PD2: I leave my site to see how big Cultural UP pictures currently in the category
http://woogar.com/web/categoria-producto/video-juegos2/

thank you very much!

http://wordpress.org/plugins/woocommerce/