Assume a situation that you are a car mechanic. As your owner went for a foreign trip, you are in-charge for the mechanic shop. As it was a Sunday, only you and a new joined guy were in the workshop. At the time of closing, you went for restroom. Meanwhile, the other guy thought that you went home. So, he locked the shop and went home. When you return back, you are shocked. As you promised your son that you will take him to a movie, you need to find the extra key as soon as possible. As you are a brilliant person, surely you will do this.