A white car of inertia \(1200 \mathrm{~kg}\) that is moving at a speed of \(7.2 \mathrm{~m} / \mathrm{s}\) rear-ends a blue car of inertia \(1000 \mathrm{~kg}\) that is initially at rest. Immediately after the collision, the white car has a speed of \(3.6 \mathrm{~m} / \mathrm{s}\). What is the coefficient of restitution for this collision?