A point mass 'm' is moved in a vertical circle of radius 'r' with the help of a string. The velocity of the mass is $\sqrt{7gr}$ at the lowest point. The tension in the string at the lowest point is
(1) 1 mg
(2) 6 mg
(3) 7 mg
(4) 8 mg
(1) 1 mg
(2) 6 mg
(3) 7 mg
(4) 8 mg