Five strokes belong to a tree, and eight seconds is the total length of the pointer.
So: 8÷(5- 1)=2 (indicating the interval, that is, knocking every two seconds)
12 point, knock 12 to indicate a tree with an interval of 2, and find the total length.
(12- 1)×2=22 (seconds), and the correct answer is 22 seconds.