[填空题]
What is the linear speed y:ajfdj1 xl gkhb2h b9- *i.k .iv9f,gf2ov v 1svr 8(6vhc(/va( y)wo4tttnpof a point (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? $m/s$