Explanation:
(C) : Given, constraints are
\(2 x+3 y \leq 18, \quad 2 x+y \leq 10, \quad x \geq 0, \quad y \geq 0\)
The feasible region is OABCO.
Also, \(\quad \mathrm{z}=9 \mathrm{x}+13 \mathrm{y}\)
Point, \(\mathrm{O}(0,0), \mathrm{z}=0\)
Point, \(\quad \mathrm{A}(5,0), \mathrm{z}=45\)
Point, \(\quad \mathrm{B}(3,4), \mathrm{z}=27+52=79\)
Point, \(\quad \mathrm{C}(0,6), \mathrm{z}=78\)

\(\therefore\) Maximum value of \(\mathrm{z}\) is 79 .