Initially, the mechanical energy of the system is all gravitational potential, given by m*g*h, where m is the person's mass (50 kg), g is the acceleration due to gravity (10 m/s²), and h is the height (5 m). This results in 2500 J. With a 36% loss due to friction, the mechanical energy at point B is 64% of 2500 J, which is 1600 J. At point C, all this energy converts to kinetic energy, given by 1/2*m*v², where v is the velocity we want to find. By equating the energies, we have 1600 = 1/2*50*v². Solving for v, we find v = 8 m/s, which is the correct answer.