Problem #57: Tower of Squares

For this tower of nine squares, determine a line passing through point P that will split the area of the nine squares into two equal parts. 
         +--+
         |  |
      +--+--+--+
      |  |  |  |
   +--+--+--+--+--+
   |  |  |  |  |  |
   P--+--+--+--+--+
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