A first-order low-pass filter of time constant $T$ is excited with different input signals (with zero initial conditions up to $t = 0$). Match the excitation signals $X, Y, Z$ with the corresponding time responses for $t \geq 0 $:

$\begin{array}{ll}\text{X:Impulse}&\text{P: $1 – e^{-t/T}$}\\\text{Y:Unit step}&\text{Q: $t – T(1 – e^{-t/T})$ }\\\text{Z:Ramp}&\text{R: $e^{-t/T}$}\end{array}$