Let x, y, z, and w be the number of units of products i, ii, iii, and iv, respectively, produced each week.
Maximize 360x + 240y + 360z + 480w
Subject to:
x + y + z = 150 (contractual obligation)
w ≤ 25 (maximum of 25 units of product iv)
x ≤ 480 (available machining time)
y ≤ 400 (available polishing time)
z ≤ 400 (available assembling time)
x, y, z, w ≥ 0 (non-negativity)
The optimal solution is x = 150, y = 0, z = 0, and w = 25, which yields a maximum profit of 90,000 birr.