A mass M moves at speed V0 perpendicular to a dumbbell at rest on a frictionless horizontal table. The dumbbell consists of two masses m at the ends of a massless rod of length L. The mass M collides elastically with one of the masses (not head-on), and afterwards it is observed that M moves perpendicular to its original direction, with speed u. What is u in terms of V0, m, and M? What is the smallest value of m (in terms of M) for which this scenario is possible?