Two identical disks, each of mass m, slide on a frictionless horizontal surface. Disk 1 moves east at 3.0m/s, and Disk 2 moves north at 4.0m/s. The disks collide and stick together. What percent of the system’s kinetic energy is lost in the collision?
a) 75%
b) 0%
c) 50%
d) 32%