Consider a system of an 85.0 kg man, his 21.0-kg dog, and the earth. The gravitational potential energy of the system increases by 2.40 103 J when the man climbs a spiral staircase from the first to the second floor of an apartment building. If his dog climbs a normal staircase from the same first floor to the second floor, by how much does the potential energy of the system increase (in J)?