A small spherical ball is suspended through a string of length l. The whole arrangement is placed in a vehicle which is moving with velocity v. Now, suddenly the vehicle stops and ball starts moving along a circular path. If tension in the string at the highest point is twice the weight of the ball then (assume that the ball completes the vertical circle)
a. v=5gl
b. v=7gl
c. velocity of the ball at highest point is gl
d. velocity of the ball at the highest point is 3gl