A mineral is added to bodies of fresh water to prevent the spread of certain freshwater parasites. The presence of those parasites threatens the health of organisms living in rivers and streams throughout the country and imperils the freshwater commercial fishing industry. The mineral is currently mined only in one particular state. In order to raise needed revenue, Congress recently enacted a statute providing for the Imposition of a $100 tax on each ton of the mineral that is mined in the United States. Because it will raise the cost of the mineral, this tax is likely to reduce the amount of the mineral that is added to freshwater rivers and streams and, therefore, is likely to have an adverse effect on the interstate freshwater commercial fishing industry. The mineral producers in the state have filed a lawsuit in federal court challenging this tax solely on constitutional grounds. Is this tax constitutional?