The city council is considering a new ordinance to require stores to provide reusable bags and eliminate disposable paper or plastic bags. In determining whether to pass the law, the city councll obtained an estimate for the expense stores would incur in offering reusable instead of disposable bags. They also obtained an estimate for the savings that would result from not having to clean up litter from disposable bags. Finally, they consulted with an environmentalist to assess the positive impact that phasing out disposable bags would have, including enhanced safety for local wildlife. In deciding whether to pass the law. the council relied on: