The 90-lb boy and 75-lb girl wald towards eachother with constant speed on a 330-lb cart with frictionless wheels. assume that the cart was at rest befor the boy and girl start walking. ith their velocities measured relative to the cart ar 4ft/s to the right and 3 ft/s to the left, respectively, determine the velocity of the cart while thy are walking. assume rightward direction is positive.