The angular velocity of a particle moving in a circle of radius `50 cm` is increased in 5 min from `100` revolutions per minute to `400` revolutions per minute. Find the tangential acceleration of the particle.
A. `60 m s^-2`
B. `pi//30 m s^-2`
C. `pi//15 m s^-2`
D. `pi//60 m s^-2`