$(18$ pts$)$ A $1\mathrm{.}50$ kg puck is sliding to the right on a frictionless, horizontal air track with a speed of $4\mathrm{.}00\frac{m}{s}.$ It has a head$-$on collision with a $0\mathrm{.}60$ kg puck that is initially at rest. Find the final velocity $($magnitude and direction$)$ of each puck if the collision is elastic.