Traverton's city council wants to minimize the city's average yearly expenditures on its traffic signal lights and so is considering replacing the incandescent bulbs currently in use with arrays of light-emitting diodes (LEDs) as the incandescent bulbs burn out. Compared to incandescent bulbs, LED arrays consume significantly less energy and cost no more to purchase. Moreover, the costs associated with the conversion of existing fixtures so as to accept LED arrays would be minimal. Which of the following would it be most useful to know in determining whether switching to LED arrays would be likely to help minimize Traverton's yearly maintenance costs? ["Whether the crews that currently replace incandescent bulbs in Traverton's traffic signals know how to convert the existing fixtures so as to accept LED arrays", 'Whether the expected service life of LED arrays is at least as long as that of the currently used incandescent bulbs', 'Whether any cities have switched from incandescent lights in their traffic signals to lighting elements other than LED arrays', "Whether Traverton's city council plans to increase the number of traffic signal lights in Traverton"]