A block of mass \(m\) slides across a horizontal frictionless surface with initial speed \(v_0\) and collides with a non-linear spring attached to a wall. The spring exerts a position-dependent restoring force of magnitude \(F(x) = k_1 x + k_2 x^3\) when compressed by a distance \(x\), where \(k_1\) and \(k_2\) are positive constants. Which of the following expressions represents the initial speed \(v_0\) required to compress the spring by a maximum distance \(D\)?