
Step 1: {Identify the corner points of the feasible region}
From the graph, the vertices of the feasible region are: \[ A(0, 50), \, B(20, 30), \, C(30, 0). \]
Step 2: {Substitute corner points into \( Z = 4x + y \)}
Evaluate \( Z \) at each vertex: \[ Z_A = 4(0) + 50 = 50,\] \[\quad Z_B = 4(20) + 30 = 110,\]
\(\quad Z_C = 4(30) + 0 = 120.\)
Step 3: {Find the maximum value}
The maximum value of \( Z \) occurs at \( C(30, 0) \), where \( Z = 120 \).
Step 4: {Verify the options}
The maximum value is \( 120 \), which corresponds to option (C).

A ladder of fixed length \( h \) is to be placed along the wall such that it is free to move along the height of the wall.
Based upon the above information, answer the following questions:
(iii) (b) If the foot of the ladder, whose length is 5 m, is being pulled towards the wall such that the rate of decrease of distance \( y \) is \( 2 \, \text{m/s} \), then at what rate is the height on the wall \( x \) increasing when the foot of the ladder is 3 m away from the wall?