Give the answer for all parts of following question:

Question: A gear with a diameter D rotates with angular velocity ? = At^2 rad/sec when t is measured in seconds.

Part A: What are the units of A?

Part B: At an arbitrary time, t, what is the magnitude of

a) The angular acceleration of the gear?

b) The tangential acceleration of a tooth on the gear?

c) The centripetal acceleration of a tooth on the gear?

Part C: Is there a time when the tangential acceleration and centripetal acceleration are equal? If so, find that time.

Could someone please show me the work and explain how to get the answer. Thanks.