The only force acting on a 2.0 kg body as it moves along a positive x-axis has an x component F_{x}=−6xN, with x in meters.The velocity at x = 3.0 m is 8.0 m/s.

a) What is the velocity of the body at x = 4.0 m?

b) At what positive value of x will the body have a velocity of 5.0 m/s?