Finding the acceleration of a lever?

Consider the rotating rod in the figure.

The length of the rod is L m.

While the rod is oriented vertically as shown, the velocity and tangential acceleration of its end point B are given as 1 m/s and -b m/s2, respectively.

Calculate the normal component of the acceleration at point B.

The values of L and b are given below.

b[m/s2] = 3.6;

L[m] = 3;

http://micko.dyndns.org/rot_rod.jpg