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.
The Cost of Trucking. $1.38 The average per mile operating cost for the trucking industry. $180,000 The average total yearly cost of operating a commercial truck. The largest operating expense is diesel fuel. A commercial truck can easily consume more than $70,000 of diesel fuel per year. Driver Salary is the second largest operating cost.