Hi there!
Recall the equation for gravitational potential energy:
[tex]U = mgh[/tex]
U = GPE (J)
m = mass (48 kg)
g = acceleration due to gravity (9.8 m/s²)
h = height (21 m)
Plug in the givens and solve.
[tex]U = (15 + 33)(9.8)(21) = \boxed{9878.4 J}[/tex]