How to?

25.2 A block of mass mi travels at speed v1 = 4.40 m/s rightward. A block of mass mz = 2 mi is at rest and the horizontal surface to the right of the block mz is rough. If the collision is completely inelastic and instantaneous, and the blocks move for 0.68 m before stopping, what is the coefficient of kinetic friction? (A) 0.12 (B) 0.16 (C) 0.19 V1 2 (D) 0.23 (E) 0.30