A mathematical problem of quadratic function in junior high school (speed) China is one of the countries with serious water shortage in the world. In order to enhance the residents' awareness of water saving, a municipal water supply company charges for the residents' water consumption by taking the household as the unit. That is to say, users with water consumption less than 10 tons (including 10 tons) per month will be charged a yuan per ton; users with water consumption more than 10 tons per month will still be charged a yuan per ton, and users with water consumption more than 10 tons will be charged a yuan per ton, The charge is B yuan per ton (b > A). If a household uses X tons of water per month, it should charge y yuan. The functional relationship between Y and X is shown in the figure 1. For the value of a, how much should a household charge for using 8 tons of water last month? 2. Find the value of B, and write the functional relationship between x > 10, y and X It is known that resident a used 4 tons more water last month than resident B. the two families charged 45 yuan. How many tons of water did they use last month?

A mathematical problem of quadratic function in junior high school (speed) China is one of the countries with serious water shortage in the world. In order to enhance the residents' awareness of water saving, a municipal water supply company charges for the residents' water consumption by taking the household as the unit. That is to say, users with water consumption less than 10 tons (including 10 tons) per month will be charged a yuan per ton; users with water consumption more than 10 tons per month will still be charged a yuan per ton, and users with water consumption more than 10 tons will be charged a yuan per ton, The charge is B yuan per ton (b > A). If a household uses X tons of water per month, it should charge y yuan. The functional relationship between Y and X is shown in the figure 1. For the value of a, how much should a household charge for using 8 tons of water last month? 2. Find the value of B, and write the functional relationship between x > 10, y and X It is known that resident a used 4 tons more water last month than resident B. the two families charged 45 yuan. How many tons of water did they use last month?

A = 1.5 yuan
Charge 12 yuan for 8 tons (charge a yuan per ton if 8 is less than 10)
15 + (20-10) * b = 35, B = 2 yuan
When x > 10, the corresponding function relation is as follows:
Y=15+(X-10)*2=2X-5