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shekib
what is the meaning of opportunity cost
It's the cost of the forgone choices when you make your decision. For instance, when you choose to read a text book for 2 hours on Sunday, you give the choice of have fun with your friends during the 2 hours.
so "having fun with your friends" instead is the cost you paid while you chose to read a textbook.
it is the best next alternative forgone. for instance a student needs a textbook, school bag and a pair of shoe. But because of financial constraint he/she boughts only the textbook. The opportunity cost is the school bag because it is the next on the list.