% The background knowledge
background([
   [wipers, not(dead_battery)],
   [radio, not(dead_battery), not(broken_speaker)],
   [ignition, key_turned, not(dead_battery)],
   [car_starts, not(out_of_gas), ignition],
   [gauge_shows_gas, not(out_of_gas), not(dead_battery)],
   [key_turned]]).

% Things that can go wrong
assumable(dead_battery).
assumable(out_of_gas).
assumable(broken_speaker).
