The graph shows data from a brick being pushed along a concrete surface. A. Some of the energy was destoryed
B. The energy was used up so it no longer exists

C. The energy transformed into thermal energy
D. The brick had no energy once the force had been removed

Part 1.  When potential energy is given off, it is exothermic.

Part 2. The activation energy can be calculated by taking the difference of the transition state enthalpy and the reactant enthalpy. With the enthalpy being defined as the sum of the ground state energy and the statistical mechanically calculated enthalpy.

Explanation: