4. The street plan of a city is a $5 \times 5$ square grid, (as shown in the figure) and there is a sweeper at point $A$. i. Find the total length of all streets.

保留了原文的换行和格式，翻译结果如上。
4. This graph has 16 odd vertices (the four inner points on each boundary) and can be divided into eight pairs of adjacent ones. Therefore, the length of the shortest cleaning route is $60+8=68$.