Solving a problem in physics section 29 point 56 mechan

56. A point moves along a plane so that it is equal to the tangential acceleration of 4 m / s2. Normal acceleration dependent on time according to AN = b ∙ t4, where b = 2 m / c6; a = 4 m / s2. Find the radius of curvature of the trajectory at time t = 2, if the initial time t0 = 0 point of rest.