\[(a)\;-5 \;m/s \quad (b)\;4\;m/s\quad (c)\;5\;m/s \quad (d)\;4\; m/s\]

Since collision is elastic $e=1=\large\frac{v_2-v_1}{u_1-u_2}$

Speed of wall will not change after collision

v be velocity of ball after collision .

Relative speed of seperation = relative speed of approach

$v_2-v_1=u_1-u_2$

$u_1=3 m/s$

$u_2=-1 m/s$

$-1-v=3-(-1)$

$v=-5m/s$

Hence a is the correct answer.

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