F.4 app. of diff

1)
http://img62.imageshack.us/img62/1021/dsc00566f.jpg
A sight-seeing lift L is descending at a constant speed of 0.5m/s from a tower. A man M stands at a distance 10m from the foot of the tower on a
horizontal ground.Find the rate of change of the distance ML with respect to time when the lift L is 25m above the ground.
ans: -0.4642m/s

2)

Initially car A is at park P and car B is 100km due to east of P. Car A moves due north away from P with a constant speed of 80km/h. Car B moves due west towards P with a constant speed of 60km/h.Find the rate of change of the distance between 2 cars respect to time after one
hour.
ans:20root5 km/h

pls shopw clear steps .thz!