Use the vector function r(t) = (t2 + 18, 3sin(t) - 3t cos(t), 3cos(t) + 3t sin(t)) where t > 0 to answer parts (a) and (b) below. (a) Find the vectors T(t) and N(t). T(t) = N(t) = (b) Find the curvature of r(t) . K(t) =