a) angular velocity = ω = 2 × π × f
where f is the frequency of rotation. In this case, f = 1 revolution / 12 seconds.
2×π = 1 revolution, so
ω = [ (2×π) / 1 revolution] × ( 1 revolution / 12 seconds)
ω = 2 π radians per 12 seconds
ω = (2/12) π radians / second = (1/6) π radians per second
b) linear velocity v = ω × r = [ (1/6) π radians per second ] × 11 cm = (11/6) × π cm / second.