If the radii of umbra and penumbra cast by an object on a wall are of the ratio 2:6, what is the area of the penumbra ring around the umbra of the latter’s radius is 40 cms?	Choose the correct choice from the following answers.
A) 40288.57 cm ^ 2	B) 40388.57 cm ^ 2	C) 40488.57 cm ^ 2	D) 40588.57 cm ^ 2	E) 40688.57 cm ^ 2

Rationale: et the radius of umbra and penumbra are 2 k and 6 k . then as given radius of umbra = 40 cm so 2 k = 40 k = 20 radius of penumbra = 20 * 6 = 120 area of penumbra ring around the umbra = area of penumbra - area of umbra 22 / 7 * [ ( 120 ) ^ 2 - ( 40 ) ^ 2 ] = 40288.57 cm ^ 2 answer : a
Answer: A