For a unit step input, the output of the first order system $\tau\dfrac{dx}{dt} + x = Ku$ (starting from rest) is $x(t) = K\left(1 - e^{-t/\tau}\right)$ Complete the table: the output $x(t)$ at $t = 0$, at $t = \tau$ and as $t \to \infty$, as a multiple of $K$. Then explain how these points are used to estimate $K$ and $\tau$ from an experimental step response.