An industrial disc of radius 0.20 m speeds up uniformly from 120 rpm to 720 rpm while rotating through 90 complete revolutions. What is the magnitude of the tangential acceleration of a point on its rim at the instant its angular speed reaches 360 rpm?
a) 1.96m s−2
b) 0.49m s−2
c) 0.98m s−2
d) 6.14m s−2