[填空题]
What is the linear speed of a po.pm3hif/ dbqjp) +ervc++ )z;ywn c c,inn+ :aa7 w8t bsv2 z..u dpscwxb))4yext (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? $m/s$