Bo Linball rolls a $8\mathrm{.}1$ kg bowling ball down the alley for the league championships. One pin is

standing still, and Bo hits it head$-$on with a $($forward$)$ unknown velocity. The $2\mathrm{.}4$ kg pin

acquires a forward velocity of $12\mathrm{.}8$ m$/$s and the bowling ball continues with a forward velocity

of $2\mathrm{.}9$ m$/$s after the collision. What is the velocity of the bowling ball before it hits the pin?