Four online shops – Hughes Home, KX Hi-Fi, Brennan Audio, and Roberts Electrical – are all selling the same model of television but at different prices. Nathan needs to get one as quickly as possible but can’t afford the most expensive. KX Hi-Fi takes longer to deliver than Brennan Audio, but is faster than Roberts Electrical. Roberts Electrical is cheaper than Brennan Audio. KX Hi-Fi costs more than Brennan Audio, but is cheaper than Hughes Home.