Answer:
The maximum value of C is 68
Explanation:
we have the following constraints
----> constraint A
----> constraint B
----> constraint C
----> constraint D
Find out the area of the feasible region, using a graphing tool
The vertices of the feasible region are
(0,0),(5,19),(5,0)
see the attached figure
To find out the maximum value of the objective function C, substitute the value of x and the value of y of each vertex in the objective function and then compare the results

For (0,0) ----->

For (5,19) ----->

For (5,0) ----->

therefore
The maximum value of C is 68