12. If a state uses the District System (described in Spotlight 11.1 on page 465) to choose its electors in a two-candidate presidential election, as Maine and Nebraska do, then some electoral permutations are impossible because the electors corresponding to the senators must not appear in a permutation before all of the electors representing the congressional districts, or after all of them. How would this affect the calculation of the Shapley-Shubik power index?