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Social networking sites such as facebook,twitter,orkut etc are used largely by teenagers. Where they can find new friends and expand their social network..it is also a means of fast,effective and cheap communication system.it allows us to share our ideas and view points with multiple individuals at the same time
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According to Lionel Robbins in the work he published in 1932 "Nature and Significance Of Economic Science"   "Economics is defined as the science which studies human behaviour as a relationship between ends and scarcity means which has alternative uses"....its considered as the most scientific definition of the whole lot in Economics