A number of us went out together to a charity fete one day. Our party consisted of 4 different professional groups, namely 25 writers, twenty doctors, eighteen dentists and twelve bank employees. We spent altogether $1,330. Later it was found that five writers spent as much as four doctors, that twelve doctors spent as much as nine dentists, and that six dentists spent as much as eight bank employees. How much did each of the four professional groups spend?