A \(1.0-\mathrm{kg}\) standard cart collides on a low-friction track with cart \(\mathrm{A}\). The standard cart has an initial \(x\) component of velocity of \(+0.40 \mathrm{~m} / \mathrm{s}\), and cart A is initially at rest. After the collision the \(x\) component of velocity of the standard cart is \(+0.20 \mathrm{~m} / \mathrm{s}\) and the \(x\) component of velocity of cart A is \(+0.60 \mathrm{~m} / \mathrm{s}\). After the collision, cart A continues to the end of the track and rebounds with its speed unchanged. Before the carts collide again, you drop a lump of putty onto cart A, where it sticks. After the second collision, the \(x\) component of velocity of the standard cart is \(-0.20 \mathrm{~m} / \mathrm{s}\) and the \(x\) component of velocity of cart \(A\) is \(+0.40 \mathrm{~m} / \mathrm{s}\). What is the inertia of the putty?