25. A manufacturer needs to place ten identical ball bearings against the inner side of a circular containe such that each ball bear
ing touches two other ball bearings, as in the picture on the
right. The (inner) radius of the container is 4 cm
(a) Find the common radius of the ball bearinga
(b) The manufacture Deeds to place a circular ring
inside the container. What is the largest possible
(outer) radius of the ring such that it is not on top
of the ball bearings and its base is level with the
base of the container?