Angular Acceleration Problem - Compact Disc

[gcombina]

During the time a compact disc (CD) accelerates from rest to a constant rotational speed of 477 rev/min, it rotates through an angular displacement of 0.250 rev. What is the angular acceleration of the CD?

I converted 477 rev/min into 49.95 rad
I converted 0.250 rev to radians which is 1.57 rad

Then I am using
ω^2 = ωø^2 + 2 α Θ
49.95/2(1.57 radians) = α
15.90 = αBUT i am not getting the answer

 

[gcombina]

the answer is 866 rad/s^2

 

[haruspex]

ω^2 = ωø^2 + 2 α Θ
49.95/2(1.57 radians) = α

ω^2 = ωø^2 + 2 α Θ