13.- A jeweler is given 4 pieces of chain with 3 links each one, and is asked to join them to create a bracelet.

When preparing the estimate, the jeweler calculates he has to solder four link, each one costs one euro so the total price would be four euros. However, the customer doesn't agree and tells him who to do it just solding three links.

How did he do it?

 

-- Solution of the riddle --