Now, we can talk about the cost utility of transportation projects; _________________ all the money to build roads, subways, airports, and train tracks. And we don't often have _________________ to build all the projects we need. So right away we must consider which _________________ and we start looking at trade-offs. For example, a city may need a bigger airport, but if the local highway isn't wide enough to carry the_________________ , then it might be better to spend money on widening the highway. So _________________.