A stone of mass m is tied to a string and is moved in a vertical circle of radius r making n revolutions per minute. The total tension in the string when the stone is at its lowest point is [Kerala (Engg.) 2001]

• A.             \[mg\]
• B.                      \[m(g+\pi \,n\,{{r}^{2}})\]
• C.             \[m(g+\pi \,n\,r)\]
• D.                      \[m\{g+({{\pi }^{2}}\,{{n}^{2}}\,r)/900\}\]