9. 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:
A.36.9 kg
B.3.696 kg
C.36 kg
D. 3.6 kg
9. 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:
A.36.9 kg
B.3.696 kg
C.36 kg
D. 3.6 kg