This problem is well-known to be NPhard [3]. For our purposes, an edge version is important: Given a subset of edges (instead of vertices), find a connected subgraph of G containing all prescribed edges with the minimal weight. This edge version of Steiner tree problem makes our problem hard even if the limit L is sufficiently large to ensure that only one inert (or chemical) car can maintain all inert roads. In this case, the set of all inert roads may be disconnected so a set of chemical roads has to be added to the inert car's plan to ensure connectivity. Finding such a set of chemical roads with the minimal weight is exactly the edge version of the Steiner tree problem. This kind of reasoning is used in Section 5 to obtain lower bounds on a minimal deadhead.

Daniel Kottke is a regular among familiar eucalyptus groves outside Stanford University's Frost Amphitheater, seeing the Dead there whenever he gets the chance. Into the '80s, the venue remains a picnic ground for Stanford research scientists and Silicon Valley characters old and new, conspiring on various levels of future building. Apple founder Steve Jobs accepts the acid from Daniel Kottke, and they go their separate ways. Spontaneously, Daniel offers his old friend a few hits of Windowpane he has in his pocket. "An old-times gesture," Daniel says.