Yolanda 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 Monday there were 5 clients who did Plan A and 3 who did Plan B. On Tuesday there were 2 clients who did Plan A and 12 who did Plan B. Yolanda trained her Monday clients for a total of 12 hours and her Tuesday clients for a total of 21 hours. How long does each of the workout plans last?