A box of mass 45 kg slides down a ramp onto a flat surface. The box slides a distance of 4.9 m across the flat surface and then stops. The coefficient of friction between the flat surface and the box is 0.39. What was the speed of the box at the base of the ramp?

6.1 m/s

0.77 m/s

3.0 m/s

19 m/s