Please see the work below.
Work Step by Step
We know that (a) $U=mg\Delta y$ We plug in the known values to obtain: $U=(65)(9.8)(11000-0.0)=7.0MJ$ (b) $U=mg\Delta y$ We plug in the known values to obtain: $U=(70)(9.8)(1600-0.0)=1.1MJ$
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