读澳大利亚图，回答问题．
– Can you tell me ____ to London? – Sure. Next month.
—Many people in big cities cannot enjoy life even though they have houses, cars and ideal jobs.
—Sub-health may partially ______ it．
如图所示的电路，R1=30Ω，R2=10Ω，开关S闭合后，电流表A的示数为0.4A，求：
（1）电源电压．
（2）通过R2的电流．
（3）干路中的电流．
