[填空题]
A softball of mass 0x5 bf8vq a93t* n mwri:y0l1nt.22/kfa/sz-9c p6ho.g vi0 kg that is moving with a speed of 8.5m/s collides head-on and elastically with another ball initially at rest. Afterward the incominhka v c./9p/sgo-fi6zg softball bounces backward with a speed of 3.7m/s Calculate
(a) the velocity of the target ball after the collision m/s
(b) the mass of the target ball. kg
(Let A represent the moving softball, and let B represent the ball initially at rest.)