2)

158<240

158*0.49=77.42 (yuan)

A: The electricity bill payable is 77.42 yuan.

3)

24 1 & lt； 307< Celebrity

240 * 0.49+(307-240) * 0.54 =153.78 (yuan)

Answer: The electricity bill payable is 153.78 yuan.

The following is a topic analysis:

This problem mainly investigates subsection calculation. 0-240 is the first gear, and within this range, the electricity consumption is 0.49 yuan per kWh, and the electricity fee = electricity consumption * 0.49; 24 1-400 is the second gear. If the power is within this range, it can be divided into two parts: 240 and 240. Among them, 240 kWh is charged according to the first standard, that is, 0.49 yuan per kWh, and the part exceeding 240 is charged according to the second standard, that is, 0.54 yuan per kWh. Electricity charge =240*0.49+ (the part exceeding 240) * 0.54; The third gear is divided into three gears by analogy. 240 kWh is charged according to the first gear, 400-240= 160 kWh is charged according to the second gear, and the part exceeding 400 is charged according to 0.79 yuan. Electricity charge =240*0.49+ 160*0.54+ (the part exceeding 400) *0.79.

Very detailed answer, please adopt, you can ask me if you don't understand.