After performing a trick above the rim of a skateboard ramp, a 56 kg skateboarder lands on the ramp 3.5 m above ground level with a downward velocity of 4.0m / s . Friction in the wheels of the skateboard and air resistance causes a loss of 9.0 * 10 ^ 2 J of mechanical energy. What the skateboarder's speed at the bottom of the ramp will be