Consider an ordinary differential equation $\dfrac{dx}{dt}=4t+4$. If $x = x_0$ at $t = 0$, the increment in $x$ calculated using Runge-Kutta fourth order multi-step method with a step size of $\Delta t = 0.2$ is

1. $0.22$
2. $0.44$
3. $0.66$
4. $0.88$