Euler's original article about the Konigsberg Bridge Problem, which is dated 1736, presents a second similar problem with two islands, four rivers flowing around them, and 15 bridges connecting various land masses, as shown in Fig.

(a) Is it possible to tour the region starting and finishing in the same area, having walked over every bridge exactly once? Either describe such a tour or explain why none is possible.

(b) Is it possible to tour the region (with perhaps different starting and stopping points), having walked over every bridge exactly once? Either describe such a tour or explain why none is possible.

A B D C F