Unfortunately for Johanna, her musket violently backfires wh…

Unfortunately for Johanna, her musket violently backfires while practicing her aim, though luckily she remains unhurt. Her musket, however, breaks into three large pieces. The stock, with a mass of 4 kg, launches behind her at a speed of 3 m/s. The firing mechcanisms, with a mass of 2 kg are launched directly to her right with a speed of 6 m/s. What is the speed of the third piece, the 3-kg barrel, immediately after the explosion?