Answer
$-0.519\frac{mm}{s}$
Work Step by Step
According to law of conservation of momentum
$p_1x+p_2x=0$
$\implies m_bv_b+m_sv_s=0$
This can be rearranged as:
$v_s=\frac{-m_bv_b}{m_s}$
We plug in the known values to obtain:
$v_s=\frac{-(0.175)(14.1)}{4.75}$
$v_s=-0.519\frac{mm}{s}$
