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.
Detailed Breakdown of Cost of Air Transportation Delay in 2007. In 2007, domestic flight delays were found to cost the U.S. economy $31.2 billion in 2007, including $8.3 billion in direct costs to airlines, $16.7 billion in direct costs to passengers, $2.2 billion from lost demand and $4.0 billion in forgone GDP. Line Item Cost Component.