Two disks sliding on a frictionless horizontal plane with opposite velocities of the same magnitude e v0

Question:

Two disks sliding on a frictionless horizontal plane with opposite velocities of the same magnitude e v0 hit each other squarely. Disk A is known to have a mass of 6 kg and is observed to have zero velocity after impact. Determine(a) The mass of disk B, knowing that the coefficient of restitution between the two disks is 0.5,(b) The range of possible values of the mass of disk B if the coefficient of restitution between the two disks isunknown.