a worked-out silver mine的用法和样例：
- Eg. This afternoon we went to the gym for a work out.
- The police worked out a plan to catch the thief.
- The manager had worked out a scheme for not paying the tax.
- The government has worked out a plan of succoring the needy.
- Professor Fang worked out a method to destroy bacteria on the seeds.
- He gets a work that gives scope for his abilities.