Four prospectors with only one lantern must walk through a mine shaft. At most, two prospectors can travel together and any prospector in the shaft must be with the lantern.  The prospectors, named Andy, Brenda, Charlie and Dan, can walk through the shaft in one, two, four, and eight minute, respectively. When two walk together, they travel at the speed of the slower prospector.  How can all four prospectors get through the mine shaft

1. Four prospectors with only one lantern must walk through a mine shaft. At most, two prospectors can travel together and any prospector in the shaft must be with the lantern.  The prospectors, named Andy, Brenda, Charlie and Dan, can walk through the shaft in one, two, four, and eight minute, respectively. When two walk together, they travel at the speed of the slower prospector.  How can all four prospectors get through the mine shaft in only 15 minutes? (On the first attempt, most get 16 minutes. There is a straight forward way to get 15.)
   
   
   
   
2. The following is an addition problem in decimal notation. Each letter represents a different digit (0-9).  What digit does each letter represent?  How did you get your foot in the door?

   A B C
+ B D B
C B C D