A rigid flywheel with a rotational inertia of \(2.0 \text{ kg}\cdot\text{m}^2\) is initially at rest. A net torque \(\tau\) is applied to the flywheel as a function of time \(t\), as shown in the graph. What is the rotational kinetic energy of the flywheel at \(t = 4.0 \text{ s}\)?