A $0.500-\mathrm{kg}$ block, attached to a spring with length 0.60 $\mathrm{m}$ and force constant $40.0 \mathrm{N} / \mathrm{m},$ is at rest with the back of the block at point $A$ on a frictionless, horizontal air table (Fig. 7.44$)$ . The mass of the spring is negligible. You move the block to the right along the surface by pulling with a constant 20.0 -N horizontal force. (a) What is the block's speed when the back of the block reaches point $B,$ which is 0.25 $\mathrm{m}$ to the right of point $A ?$ (b) When the back of the block reaches point $B$ , you let go of the block. In the subsequent motion, how close does the block get to the wall where the left end of the spring is attached?