【Question 9】
There are six chains, each with four links (as shown in the figure). It takes 1 minute to open a link and 3 minutes to close an opened link. Now, to connect these 24 links into one chain, at least $\qquad$ minutes are needed.
【Analysis and Solution】
Open 4 rings of a chain, use these 4 rings to connect the remaining five chains; it will take at least $(1+3) \times 4=16$ minutes.