% Find internal temperatures. p. 60.

m=[    1, -1/4,    0, -1/4,    0,    0,    0,    0,    0;
    -1/4,    1, -1/4,    0, -1/4,    0,    0,    0,    0;
       0, -1/4,    1,    0,    0, -1/4,    0,    0,    0;
    -1/4,    0,    0,    1, -1/4,    0, -1/4,    0,    0;
       0, -1/4,    0, -1/4,    1, -1/4,    0, -1/4,    0;
       0,    0, -1/4,    0, -1/4,    1,    0,    0, -1/4;
       0,    0,    0, -1/4,    0,    0,    1, -1/4,    0;
       0,    0,    0,    0, -1/4,    0, -1/4,    1, -1/4;
       0, -  0,    0,    0,    0, -1/4,    0, -1/4,    1];

c=[10;5;10;5;0;5;30;25;30];

m\c




