Electric Power Agency - Relay Network: The agency is maintaining an electric power relay network which is represented by a given binary tree T with n nodes. The root r of T represents the power distribution center which also acts as a relay node like the other nodes in T . Each node xT has an associated operational cost, denoted cost[x] , which is a positive real number. Nodes may be turned on or off. A node that is turned off incurs no cost, but a node that is turned on incurs its associated operational cost. The agency has a limited operational budget and