sky Entertainment is a provider of$$ cable, internet, and$$ on$-$demand video services. currently sends monthly bills to its customers via the postal service. Because of a concern for the environment and recent increases in postal$$ rates, sky management is considering offering an option to its customers for paperless billing. In addition to saving$$ printing, paper, and postal$$ costs, paperless billing will save energy and water$($through reduced paper$$ needs, reduced waste$$ disposal, and reduced transportation$$ needs$).$ While sky would like to switch to$100\%$ paperless$$ billing, many of its customers are not comfortable with paperless billing or may not have Web$$ access, so the paper billing option will$$ remain, regardless of whether sky adopts a paperless billing system or not.