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 average cost per domestic trip in North America will increase by 1.2% to $1,002 in 2009, the company estimates. Last year, American Express estimated a 3.9% increase for 2008.The average cost per international trip for North American business travelers will increase by 3.5% to $3,452. Last year, American Express estimated a 7.8% increase for 2008.Travel costs will not change significantly in 2009, says Herve HervÃ©, sedky vice president Of American, Express Global Advisory. serviceshe average cost per domestic trip in North America will increase by 1.2% to $1,002 in 2009, the company estimates. Last year, American Express estimated a 3.9% increase for 2008.