In a grid of wires, the temperature at exterior mesh points is maintained at constant values as shown in the figure. When the grid is in thermal equilibrium, the temperature at each interior mesh point is the average of the temperatures at the four adjacent points. For instance, _ T2+T3+2I2l 160 T 1 4 Find thetemperatures T1, T2, T3, T4, when the grid is in thermal equilibrium. -160 20 -160 20 1 1 410 TA 150 -250 150