Two blocks of masses \(m_1\) and \(m_2\) slide to the right along a horizontal surface with a uniform coefficient of kinetic friction \(\mu\). Block 1 is initially traveling faster than block 2 and catches up to it, colliding and sticking to block 2 at time \(t_c\). The combined blocks continue sliding to the right until coming to rest at time \(t_f\). Which of the following graphs best represents the position of the center of mass of the two-block system, \(x_{\text{cm}}\), as a function of time \(t\) between \(t = 0\) and \(t_f\)?