In a grid of wires, the temperature at exterior mesh points is maintained at constant va...

In a grid of wires, the temperature at exterior mesh points is maintained at constant values (in ºC), as shown in the accompanying figure. When the grid is in thermal equilibrium, the temperature T at each interior mesh point is the average of the temperatures at the four adjacent points. For example,

Find the temperatures T₁, T₂, and T₃ when the grid is in thermal equilibrium.