A railroad tank car rolls on a track at $2\mathrm{.}60$ m$/$s toward two identical coupled tank cars, which are rolling in the same direction as the first, but at a speed of $1\mathrm{.}20$ m$/$s$.$ The first reaches the second two and all couple together. The mass of each is $2\mathrm{.}80104$ kg$.$

a. What is the speed $($in m$/$s$)$ of the three coupled cars after the first couples with the other two? $($Round your answer to at least two decimal places.$)$ 

b. Find the $($absolute value of the$)$ amount of kinetic energy $($in J$)$ converted to other forms during the collision.