Auto featured image in posts of the same category

Hey guys, I’ve been searching high and low for a solution to automatically set a same featured image in all the posts of a category. Reason why is because, a url redirection was done a few days ago and there are over 80 categories, and over 3000 posts; and it’ll be tedious and time consuming if I were to set a feature image post by post.

I’m using Mingle theme if that intel helps..lol.
Thanks in advanced. <3

;D