A spacecraft of mass \(m\) orbits a planet of mass \(M\) in a uniform circular orbit of radius \(r_1\). Thrusters fire to transition the spacecraft into a new, smaller uniform circular orbit of radius \(r_2\), where \(r_2 < r_1\). Which of the following correctly identifies the sign of the net work done by the thrusters on the spacecraft-planet system during the transition and the sign of the change in the spacecraft's kinetic energy, \(\Delta K = K_2 - K_1\)?