Let the manufacturer produces x pedestal lamps and y wooden shades; then time taken by x pedestal lamps and y wooden shades on grinding/cutting machines = (2x + y) hours and time taken on the sprayer = (3x + 2y) hours.
Since, grinding/cutting machine is available for at the most 12 hours.
∴ 2x + y ≤ 12
and sprayer is available for at most 20 hours.
Thus, we have
3x + 2y ≤ 20
Now, profit on the sale of x lamps and y shades is,
Z = 5x + 3y.
So, our problem is to find x and y so as to
Maximise Z = 5x + 3y …...(i)
Subject to the constraints:
3x + 2y ≤ 20 …....(ii)
2x + y ≤ 12 …....(iii)
x ≥ 0 ….....(iv)
y ≥ 0 .,....…(v)
The feasible region (shaded) OABC determined by the linear inequalities (ii) to (v) is shown in the figure. The feasible region is bounded.
Let us evaluate the objective function at each corner point as shown below:
We find that maximum value of Z is Rs 32 at B(4, 4). Hence, manufacturer should produce 4 lamps and 4 shades to get maximum profit of Rs 32.