1. What is the depth of the node indicated with an <-
     ,----
     |    ()
     |   /  \    
     |  ()   ()
     |      /  \
     |     ()  () 
     |    /
     |   ()
     |  /  \
     | ()   () <-
     |   \
     |    ()
     `----


  2. What is the height of the following tree?

     ,----
     | ()
     |   \
     |    ()
     `----


  3. What is the height of a tree with NO nodes?