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..., which is worth of about 7.1 billion dollars.

It seems that "of" is not needed.

worth /ˈwɚθ/ preposition

 

^{1 a— used to indicate the value of something
▪ a ruby worth five million dollars
▪ This painting is worth a fortune.
▪ You should be paid what your labor is worth
▪ Each correct answer is worth five points.}

^{b: having money and possessions equal in value to (an amount)
▪ an actor worth several million dollars
▪ The corporation is worth billions of dollars.}

^{Source: http://www.learnersdictionary.com/search/worth}