[填空题]
What is the linear speed of a 1 oiyg s;kz(od88c2rob,)odipoint un,y7 g5mg8 abi),zlf (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? $m/s$