A hollow iron pipe is 21 cm long and its external diameter is 8 cm. If the thickness of the pipe is 1 cm and iron weighs 8 g/cm3 , then the weight of the pipe is
Choose the correct choice from the following
A) 3.6 kg	B) 3.696 kg	C) 36 kg	D) 36.9 kg	E) none of these

Rationale: "explanation : external radius = 4 cm , internal radius = 3 cm . volume of iron = [ ( 22 / 7 ) × ( 42 - 32 ) × 21 ] cm 3 = 462 cm 3 weight of iron = ( 462 x 8 ) gm = 3696 gm = 3.696 kg answer : b"
Answer: B