A toy train rolls around a horizontal 1.0--diameter track. The coefficient of rolling friction is 0.10. What is the magnitude of the train's angular

A toy train rolls around a horizontal 1.0--diameter track. The coefficient of rolling friction is 0.10. What is the magnitude of the train's angular acceleration after it is released? How long does it take the train to stop if it's released with an angular speed of 30rpm?