Consider two blocks A and B of masses $m_1=10 \mathrm{~kg}$ and $m_2=5 \mathrm{~kg}$ that are placed on a frictionless table. The block A moves with a constant speed $v=3 \mathrm{~m} / \mathrm{s}$ towards the block B kept at rest. A spring with spring constant $\mathrm{k}=3000 \mathrm{~N} / \mathrm{m}$ is attached with the block $B$ as shown in the figure. After the collision, suppose that the blocks A and B , along with the spring in constant compression state, move together, then the compression in the spring is, (Neglect the mass of the spring)