The potencial energy is given by the following formula:

Where "m" is the mass, "g" is the acceleration of gravity, and "h" is the height. Since the height is below the reference point it has a negative sign. Replacing we get:

Solving the operation:

The negative sign indicates that the object is below the zero point.
b. Since the work is equivalent to:

The force that acts on the object is equivalent to its weight and the distance the height, therefore:

Replacing:
![\begin{gathered} W=(3\operatorname{kg})(9.8(m)/(s^2))(10m) \\ W=294J \end{gathered}]()