Study the scenario.

A box is initially at the top of a slide, storing 80 J of gravitational energy. The isolated system includes the box, slide and earth.

As the box slides down the frictionless slide, what happens to the total energy of the system?

The isolated system stores slightly less than 80 J of total energy, and it is converted to a different form of energy
The isolated system stores 80 J of total energy, but it is converted to a different form of energy.
The total energy of the isolated system decreases to 0 once the box reaches the bottom of the slide.
The total energy of the system increases to more than 80 J of energy as it gains other forms of energy