A communication company accumulates a communication time or the amount of communication for a call when the call is received, and provides additional service such as discount for a called party according to an accumulated communication time or the accumulated amount of communication. Another example of additional service is discount made according to whether a first communication company providing communication service between a called party and a first switching office and a second communication company providing communication service between a calling party and a second switching office are identical.

 
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> Color separating-combining optical system, image display optical system, and projection image display apparatus

~ 00350