ANSWER:

" Rob will place the documents in the mail box and lock it with his lock.
Later Ben comes and locks the mailbox with his own new lock for which he has the key.
Then Rob comes and removes his lock. Since the box is locked with Ben's lock, the documents will remain safe.
Now, Ben comes removes his lock, opens the mail box and takes away the documents..

Is that clear?

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Graceynapple
SeecretGal

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