Alan turned his laptop on. The fan started humming loudly. It was a loud, steady hum. Alan could hear the hum from ten feet away. It hummed until he turned his laptop off. He told his friend about the hum. His friend said there was dust near the fan. He told Alan to blow out the dust. Alan went to Staples. "Do you sell compressed air?" he asked. The worker showed him a two-pack for $10. "Can't I buy just one can for $5?" Alan asked. The worker said no. Alan bought the two-pack. Why not make us buy a SIX-pack, he wondered angrily. He went home. He blew the compressed air into the vents near the computer fan. He turned on his vacuum cleaner. He vacuumed the vents for about five minutes. He turned on his laptop. It was as quiet as a mouse! Alan hummed a happy tune.