The correct option is C 23mgR
The gravitational potential energy at a point, on or above the earth's surface, is given by,
U=−GMmr
Here, r is the distance of the mass m from the centre of earth.
⇒ ΔU=Uf−Ui
=−GMmR+2R−(−GMmR)
=GMmR(1−13)
=23mgR
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Hence, (C) is the correct answer.