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.
Defense Travel System has few defenders. The Defense Travel System has cost taxpayers almost $500 million in the past eight years. Lawmakers are vocal critics of the program, and many Defense Department executives, travel company officials and employees who are directed to use the system are dissatisfied with it. DOD executives say DTSâ problems are symptomatic of a broken process for managing travel departmentwide.