Name the character in Mahabharat who was blessed with the 'divine vision' to see the Mahabharata battle and explain it scene by scene to the blind king Dhritarashtra.
Two circles of same radius intersect each other at P and Q. If the length of the common chord is 30 cm and distance between the centres of the two circlesis 40 cm, then what is the radius (in cm) of the circles?