[填空题]
What is the linear speejsp-+sj3 hfr47.jsr l, u6g tld of a pointu7zi s)ivh5i(zoem2ng;1+j w5/nlo i (a) on the equator, $m/s$ (b) on the Arctic Circle (latitude 66.5$^{\circ} $ N), $m/s$ (c) at a latitude of 45.0$^{\circ} $ N, due to the Earth’s rotation? $m/s$