$T=2 \pi \sqrt{\frac{4 \ell}{g}}$
$T=2 \pi \sqrt{\frac{4 \times 4}{g}}$
$T=2 \pi \frac{4}{\pi}=8 s$
($A$) The amplitude of oscillation in the first case changes by a factor of $\sqrt{\frac{M}{m+M}}$, whereas in the second case it remains unchanged
($B$) The final time period of oscillation in both the cases is same
($C$) The total energy decreases in both the cases
($D$) The instantaneous speed at $x_0$ of the combined masses decreases in both the cases
$\mathrm{y}=\mathrm{A}_{0}+\mathrm{A} \sin \omega \mathrm{t}+\mathrm{B} \cos \omega \mathrm{t}$
Then the amplitude of its oscillation is given by

(Round off to the Nearest Integer)