A wheel's angular acceleration is constant. Initially its angular velocity is zero. During the first 1.0-s time

Question:

A wheel's angular acceleration is constant. Initially its angular velocity is zero. During the first 1.0-s time interval, it rotates through an angle of 90.0°.
(a) Through what angle does it rotate during the next 1.0-s time interval?
(b) Through what angle during the third 1.0-s time interval?