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.
Following two rounds of cuts in Chicago, the average cost of an Uber trip fell from $14.25 in December 2013 to just $11 in 2014 â a decline of nearly 23 percent.hile Uber doesnât provide data on average miles driven per hour, we can make a few educated guesses based on the information provided. The US government has deemed the average cost of operating a vehicle to be $0.56 per mile, $0.235 of which are variable costs based on mileage.