Projectile launched vertically from moon at 1380 m/s

[Brad2007]

Question: A projectile is launched vertically from the surface of the Moon with an initial speed of 1380 m/s. At what altitude is the projectile's speed two-thirds its initial value?

I don't really know where to start there is so little information. We went over escape velocity in class, but I don't think this is it.

 

[Integral]

Could you solve this problem if it were on the earth?

If so what is the difference between the Earth and moon?