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.
DENVER (August 23, 2017) â Owning and operating a new vehicle in 2017 will cost a driver an average of $8,469 annually, or $706 each month, per a new study from AAA. The annual evaluation of driving costs reveals that small sedans are the least expensive vehicles to drive at $6,354 annually, however small SUVs ($7,606), hybrids ($7,687) and electric vehicles ($8,439) all offer lower-than-average driving costs to U.S. drivers.