[填空题]
What is the linear speed of a poi) aal.jabg48ys 8l*p ,hnvz1f ntj0-i:u,p uu *vgmk1;y2pne cg (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? $m/s$