Architecture Puzzler #223

In contemporary mirror manufacture, what reflective material is most commonly applied to the back surface of the glass?

On March 26, 2000 an implosion lasting 16.8 seconds reduced Seattle’s Kingdome to a pile of rubble. It took considerably longer to remove the pile that measured 12 to 23 feet (3.6 to 7.0 meters) deep at its perimeter. What was the approximate cost of the entire demolition contract?