It is required to fix a pipe such that water flowing through it at a speedof 7 metres per minute fills a tank of capacity 440 cubic metres in 10 minutes. The inner radius of the pipe should be :

• A. $\sqrt 2 \,m$$
• B. $ 2 \,m$$
• C. $\frac{1}{{2 }}\,m$$
• D. $\frac{1}{{\sqrt 2 }}\,m$$