A 20 metric ton train moves toward the

A 20 metric ton train moves toward the
south at 70 m/s.
At what speed must it travel to have two
times its original momentum?A metric ton
is 1000 kg.
At what speed must it travel to have a
momentum of 5 × 10
5
kg · m/s
If there were a speed limit for this train as
it traveled through a city,but not a weight
limit,what mass must be added to the train
to slow it down to 10 m/s while at the same
time keeping the momentum the same as in
the second part?
Answer in units of kg