读澳大利亚气候分布图，回答下列问题．

阅读下面语篇并根据语篇内容回答问题
    A train stopped at a small station. A man on the train looked out of the window and saw a woman. The woman was selling cakes, and the people from the strain bought them. The man wanted to buy a cake, but the woman was far away from him. It was raining, and he didn't want to go out. Suddenly he saw a boy. The boy was walking on the flatform（月台）not far from him. “Come here.” He said to the boy, “Do you know how much each of the cakes is?” “Five cents（分）.” The boy answered. The man gave the boy ten cents and asked him to buy two cakes. “One is for me and the other is for you” he told the boy. Some minutes later, the boy came back. He was eating a cake. He gave the man five cents and said, “There was only one    cake left（剩下的）.”

求：

如图，在平面直角坐标系xOy内，第1象限存在沿y轴负方向的匀强电场，第Ⅳ象限以ON为直径的半圆形区域内，存在垂直于坐标平面向外的匀强磁场，磁感应强度为B．一质量为m、电荷量为q的带正电的粒子，从y轴正半轴上y=h处的M点，以速度v₀垂直于y轴射入电场，经x轴上x=2h处的P点进入磁场，最后以速度v垂直于y轴射出磁场．不计粒子重力．求：