5.  A man standing at a point P is watching the top of a tower, which makes an angle of elevation of 30° with the man’s eye. The man walks some distance towards the tower to watch its top and the angle of the elevation becomes 60°. What is the distance between the base of the tower and the point P?  (a)4√3 units  (b)8 units  (c)12 units  (d)Data inadequate 

Answer is: DOne of AB, AD and CD must have been given.So, the data is inadequate.