A disc rotates at 60 rev/min around a vertical axis. A body lies on the disc at the distance of 20cm from the axis of rotation. What should be the minimum value of coefficient of friction between the body and the disc, so that the body will not slide off the disc

• A

  $8{\mathrm{\pi }}^2$

• B

  $0.8{\mathrm{\pi }}^2$

• C

  $0.08{\mathrm{\pi }}^2$

• D

  $0.008{\mathrm{\pi }}^2$