Assistant: Can I help you, Miss White?

Miss White: Yes. I want a pair of  sandals, please.

Assistant: What size?

Miss White: Size ten .

Assistant: How about this pair? They are black. They are good.

Miss White: How much are they?

Assistant: They are 160 yuan.

Miss White: Oh. They are too expensive.

Assistant: These brown sneakers are cheaper. They're 30 yuan.

Miss White: OK. I will take them.

①求通过电阻R₁的电流I₁____。

②求电阻R₂的阻值____。

③现用标有“20Ω  2Α”字样的滑动变阻器R₀替换电阻R₁或R₂中的一个，请在不损坏电路元件的情况下，通过移动滑片P，使电路的功率变化范围最大，并求出此范围____。

I ____ ____ ____I will succeed.