Melissa the trainer has two solo workout plans that she offers her clients: Plan A and Plan B. Each client does either one or the other (not both). On wednesday there were 5 clients who did Plan A and 3 who did Plan B. On thursday there were 7 clients who did Plan A and 9 who did Plan B. Melissa trained her wednesday clients for a total of 6 hours and her thursday clients for a total of 12 hours. How long does each of the workout plans last?