Sarah is interested in making several changes to the roof of her apartment building to make the building more energy-efficient. The building is three stories tall with a flat roof in an urban area. Because it reaches above the tree line, it receives a significant amount of sun throughout the year. Provide two examples of changes that Sarah could make to her roof to improve the energy efficiency of the building. For each change, make sure to state in what ways it would improve the building’s energy efficiency. Then list the materials Sarah will need and any workers she will need to hire.