Parts of the teeth include: 1  Enamel: The hardest, white outer part of the tooth. Enamel is mostly made of calcium phosphate, a rock-hard mineral. 2  Dentine: A layer underlying the enamel. Dentine is made of living cells, which secrete a hard mineral substance.  Pulp: The softer, living inner structure of teeth.
Though they vary significantly, transportation costs accounted for 40% of the average overall cost of coal delivered at electric power plants in 2010. On average, nominal U.S. rail rates for shipping coal grew from $11.83 to $17.25 per short ton from 2001 to 2010.
Total Trip Costs. Adding up the cost of gas, food and lodging, a typical road trip from New York to Los Angeles actually has decreased slightly in price, from $1,159.20 to $1,150.70, between 2015 and 2016. A moderate decrease in gas prices more than cancels out slight increases in food and lodging costs.