The minimum step-size required for a Delta-Modulator operating at $32 \mathrm{~K}$ samples/ $\mathrm{sec}$ to track the signal (here $u(t)$ is the unit-step function)
$\begin{array}{l}x(t)=125 t(u(t)-u(t-1))+(250-125 t)(u(t-1) -u(t-2)) \end{array}$
so that slope-overload is avoided, would be
- $2^{-10}$
- $2^{-8}$
- $2^{-6}$
- $2^{-4}$