[填空题]
By what factor does t+ r1ufj ;i/a7sks (ufshe rotationae) + p:dw. sm3mcsl1dwuxbo, +l kinetic energy change when the star in Problem 56 collapses toc)3: p 1+mlusw+d,oesdm. bxw a neutron star? $\dfrac{\text{KE}_{\text{final}}}{\text{KE}_{\text{initial}}} = $ $ \times 10^9$
