To search for a solution several properties of the network might help:• Using twice (or an even number of times...) a switch doesn't help: Any second switch action "undoes" the first• The effect of using any switches X and Y (in this order), is the same of using Y before X.Thus, the number of sequences of switches to try is in fact limited: At worst all the subsets of the seven switches. There are 128 subsets of a set of 7 elements; it is also worth noting that each of these sequences has a different total effect on the network. Therefore, since there are only 27 (= 128) different configurations of the network, each of them can be obtained from any initial configuration.