A block of mass 0.49kg starts from rest at point A and slides down a frictionless hill of height h. At the bottom of the hill it slides across a horizontal piece of track where the coefficient of kinetic friction is 0.28. This section (from points B to C) is 3.60m in length. The block then enters a frictionless loop of radius r= 2.58m. Point D is the highest point in the loop. The loop has a total height of 2r.

Question

A block of mass 0.49kg starts from rest at point A and slides down a frictionless hill of height h. At the bottom of the hill it slides across a horizontal piece of track where the coefficient of kinetic friction is 0.28. This section (from points B to C) is 3.60m in length. The block then enters a frictionless loop of radius r= 2.58m. Point D is the highest point in the loop. The loop has a total height of 2r. 
What is the minimum kinetic energy for the block at point B in order to have enough speed at point D that the block will not leave the track?
What is the minimum height from which the block should start in order to have enough speed at point D that the block will not leave the track?