[填空题]
(a) What is the angular momentum of wlj:dkk hz1:i)46 mc . qba-vta figureh apw,b 8iz vlwr*: dx*8-f)rz skater spinning at 3.5 $rev/s$ with arms in close to her body, assuming her to be a uniform cylinder with a height of 1.5 m, a radius of 15 cm, and a mass of 55 kg? $kg \cdot m^2$ (b) How much torque is required to slow her to a stop in 5.0 s, assuming she does not move her arms? $m \cdot N$