The good roads amendment requires that percent of road-user fees be spent on building and maintaining roads.

75 percent

Explanation:

The good roads amendment is a law enacted by legislatives in the USA states that ensure maintenance of roads in each state as well as interconnecting roads.

It states, amist other things, that 75% of road user fees collected through tolls and other means are spent on road maintenance.

Cheers.

answermarginal cost;

answer(b) equal; set period;