How long will it take them to glide to the edge of the rink?

At the center of a 50 m diameter circular ice rink, if a 77 kg skater traveling at 2.3 m/s and then collides with a 63 kg skates traveling at 3.7 m/s. This is how long it will take them to glide to the edge of the rink:

Speed after the collision= √{[77(2.3)77^2] + [63(3.7)^2]} / (77+63)=2.09 m/s

For them to be able to get to the edge which is 50 m away it will take them 23.9 seconds.

there are no contact forces mentioned on the list of choices that you've provided.