题目
Problem
A postman needs to deliver letters to all of the streets in the network shown in Figure 3. The number on each arc is the length, in metres, of the corresponding street.
The total length of the network is 261 m.
The postman must travel along each street at least once, starting and finishing at A.
(a) Determine the length of the shortest route for the postman. You must make your method clear.
(5)
The postman now learns that street FG has been closed for maintenance.
(b) Determine the length of the shortest route for the postman in this changed network.
(5)
题目中文翻译
一名邮递员需要将信件送到图 3 所示网络中的所有街道。每条弧上的数字是对应街道的长度（单位：米）。
网络总长度为 261 m。
邮递员必须每条街道至少经过一次，从 A 出发并回到 A。
(a) 确定邮递员最短路线的长度。必须清楚说明方法。
邮递员现在得知街道 FG 因维护而关闭。
(b) 确定在此变化后的网络中邮递员最短路线的长度。