N=[tex](c - \frac{7}{54} ) - (3c - \frac{1}{2}c {}^{2} - \frac{5}{6} + \frac{5}{36} c) = \frac{1}{2}c {}^{2} - \frac{77}{36} c + \frac{19}{27} [/tex]
=[tex]( \frac{1}{9} \times 9c - \frac{1}{9} \times \frac{7}{6} ) - \frac{3c}{5} \times 5 + \frac{3c}{5} \times - { \frac{5}{6}c } - \frac{1}{6} \times 5 - \frac{1}{6 } \times - \frac{5}{6} c[/tex]
