The book example uses 3 factors, Capital (K), Labour (L), and Land (T)
One good (cloth, C) only uses labour, but not land and food use land, but not capital.
The production function (for cloth) is given by: Q_c=Q_c(K,L_c)
The production function (for food) is given by: Q_f=Q_f(T,L_c)
Where Lc+Lf=L