Before revision:  Our theoretical predictions can be tested experimentally by a straightforward modification of the protocol for controlling the force in the optical trap set up that was used in the original experiments under force-clamp conditions .
After revision:  Our theoretical predictions can be tested experimentally by a straightforward modification of the protocol for controlling the force in the optical trap set up that was used in the original experiments under force-clamp and force-ramp conditions. From numerical studies of the model we predict the trends of variation of the mean life time and mean rupture force with the increasing number of MTs in the bundle. Both the mean life time and the mean rupture force display nontrivial nonlinear dependence on the maximum number of MTs that can attach simultaneously to the same kt .