Step 1 :Define the function to be maximized or minimized as \(P=20x-4y+64\).
Step 2 :Define the constraints as \(7x+9y \leq 63\), \(0 \leq y \leq 4\), and \(0 \leq x \leq 5\).
Step 3 :Find the vertices of the feasible region defined by the constraints.
Step 4 :Substitute the coordinates of the vertices into the function \(P\).
Step 5 :Compare the function values to find the maximum and minimum values and the corresponding values of \(x\) and \(y\).
Step 6 :The maximum value of the function is \(100\) and it occurs where \(x=5\) and \(y=0\).
Step 7 :The minimum value of the function is \(16\) and it occurs where \(x=0\) and \(y=4\).
Step 8 :\(\boxed{\text{Final Answer: The maximum value of the function is } 100 \text{ and it occurs where } x=5 \text{ and } y=0. \text{ The minimum value of the function is } 16 \text{ and it occurs where } x=0 \text{ and } y=4.}\)