A2.8 kg block moving along the x axis is acted upon by a single horizontal force that varies with the block’s position according to the equation fx = a x2 + b , where a = 8 n/m2 , and b = −3.9 n. at 1.7 m, the block is moving to the right with a speed of 3.8 m/s. determine the speed of the block at 2.5 m. answer in units of m/s.