A rope of negligible mass passes over a pulley of negligible mass attached to the ceiling, as shown in figure. One end of the rope is held by Student A of mass 70 kg, who is at rest on the floor. The opposite end of the rope is held by Student B of mass 60 kg, who is suspended at rest above the floor. The minimum acceleration a₀ with which the Student B should climb up the rope to lift the Student A upward off the floor. 

• A

  $\frac{1}{3}\mathrm{m}/{\mathrm{s}}^2$

• B

  $\frac{2}{3}\mathrm{m}/{\mathrm{s}}^2$

• C

  $\frac{4}{3}\mathrm{m}/{\mathrm{s}}^2$

• D

  $\frac{5}{3}\mathrm{m}/{\mathrm{s}}^2$