Answer:
'
Step-by-step explanation:
It is given that,
Mass of the plunger,

Mass of the bullet,
Initially both plunger and the bullet are at rest,

Final speed of the bullet,

Let
is the final speed of the plunger. Using the conservation of momentum to find it. The equation is as follows :

Since,





So, the recoil velocity of the plunger is 8.19 m/s. Hence, this is the required solution.