I don’t know what book you’re talking about so I can’t help but have a look online, you may be able to find it if you search up the book name and look around a few websites
Answer:

Explanation:
The angular momentum of the pulsar is given by:

where
is the mass of the pulsar
is the radius
is the angular speed
Given the period of the pulsar,
, the angular speed is given by

And so, the angular momentum is
