Two objects, x and y, have equal mass and are moving with speeds u and 3u

Two objects, x and y, have equal mass and are moving with speeds u and 3u respectively. Their kinetic energies k_x and k_y are related as 

1. K_x = K_y
2. 2k_x= k_y 
3. 9k_x = k_y
4. 3k_x = k_y