A 1.0 kg lump of clay is sliding to the right on a frictionless surface with speed 2m/s. It collides head-on and sticks to a 0.5 kg metal sphere that is sliding to the left with speed 4 ms. What is the kinetic energy of the combined objects after the collision?

(a) 6j
(b) 4j
(c) 2j
(d) 0j