What is the angular momentum of a rotating disk and how do you calculate it?

[JSmithDawg]

Homework Statement

The 1.8kg , 5.2-cm-diameter disk is rotating as shown. What is the angular momentum of the disk about the axle?

Homework Equations

L=Iω=(mr^2)ω

The Attempt at a Solution

r=.026m
m=1.8 kg
ω=600rpm*(1minute/60seconds)*(2pi radians/1rotation) = 62.83 rad/sec

L=(1.8kg * .026m^2) * 62.83 rad/sec = .076 (kg*m^2/s). I think this is correct, but my online quiz says that the answer is .038. What am I doing wrong?

 

[Nathanael]

What is the rotational inertia of the disk?