$(a)\;v_{1} =v_{2}\qquad(b)\;v_{1}=m_{2} \sqrt{\large\frac{2G}{d(m_{1}+m_{2})}}\;v_{2}=m_{1} \sqrt{\large\frac{2G}{d(m_{1}+m_{2})}}\qquad(c)\;v_{1}=m_{1} \sqrt{\large\frac{2G}{d(m_{1}+m_{2})}}\;v_{2}=m_{2} \sqrt{\large\frac{2G}{d(m_{1}+m_{2})}}\qquad(d)\;v_{1}=m_{2} \sqrt{\large\frac{2G}{m_{1}}}\;v_{2}=m_{1} \sqrt{\large\frac{2G}{m_{2}}}$