$6\mathrm{.}4$: Finally, verify the equation above for a situation where cart $B$ has more mass than cart $A.$ Remove the $500-$gram black bar mass from cart A$,$ and increase the mass of cart $B$ by placing the mass on it$.$ Again, with the increased mass of cart $B,$ predict the speed of cart A after the collision in terms of its speed before the collision, and test your prediction.