Describe the facts about the projects that would dictate which criterion is appropriate and indicate which project is preferable under each circumstance.

2. Highway departments and airports need some substance that will melt ice from roads and runaways so that traffic may continue to flow safely when winter storm hit. Here are some options that are available:

Road salt costs about $30 per ton, and it works fast. More than 10 million tons are spread each year in the United States. It is corrosive to concrete, asphalt, and metal, thus eating road, bridges, and car bodies. It contaminates drinking water and kills trees and plants. Studies suggest that this damage costs from $600 to $1,000 per ton of salt to correct.

Calcium magnesium acetate, a commercial deicer, is made from limestone and vinegar. It costs about $650 per ton and takes about 15 minutes longer than salt to melt large ice patches. It usually lasts somewhat longer. Scientists think it may actually do some good for sol and plant life, and it is not corrosive.

Contrast financial cost and social cost involved with using these products. Which cost should be used for government decision-making? Why?