[填空题]
By what factor does the rotationalyc-y jg4 c;8t;sv;z lg kinetic enera.whz-w,l kr f)rc o, bq/g-tk,i8sh0gy change when the star in Problem 56 coll krqh/ tw,a.hgfwl s,z -ib,co -)rk80apses to a neutron star? $\dfrac{\text{KE}_{\text{final}}}{\text{KE}_{\text{initial}}} = $ $ \times 10^9$
