Answer
The magnitude of the angular momentum is $~1.39\times 10^7~kg~m^2/s$
Work Step by Step
We can express the angular speed in units of rad/s:
$350~rpm~\times \frac{2\pi~rad}{1~rev}\times \frac{1~min}{60~s} = 36.65~rad/s$
We can find the angular momentum:
$L = I~\omega$
$L = MR^2~\omega$
$L = (5.6\times 10^4~kg)(2.6~m)^2~(36.65~rad/s)$
$L = 1.39\times 10^7~kg~m^2/s$
The magnitude of the angular momentum is $~1.39\times 10^7~kg~m^2/s$.