[单选题]
You (50-kg mass) skate 9hcp vseq4-i34r42ro 9cb.3v os 7r*oq exedw on ice at 4.0 m/s to greet your friend (40-kg mass), who is standing still, with open arms. As you collide, while holding each other, with what speed do you both mov49 xr2redc*ov7 o4qow.res3 be off together?