A spring with a constant of $4 \frac{k g}{s^{2}}$ $4 (kg)/(s^2)$ is lying on the ground with one end attached to a wall. An object with a mass of $4 k g$ $4 kg$ and speed of $9 \frac{m}{s}$ $9 m/s$ collides with and compresses the spring until it stops moving. How much will the spring compress?