Current Profit Equation
Profit Income = 400x + 300y
x: the number of rods manufactured
y: the number of pillars manufactured

Constrains
x≥20 The company can sell at least 20 rods and be integers
y≥0 The rods production must be positive and integers

x+2y ≤ 120 drillng hours up to 120 hours/week,
1 for each rod, 2 for each pillar
x + y≤80 grinding hours up to 80/week
1 hour for each rod, same for each pillar
x+0.6y≤72 polishing hours up to 72/week
1 hour for each rod, 36 min/0.6 hr for each pillar

Feasible Region

a(y) = y ≥ 0
b(x) = x ≥ 20
c(x, y) = x + (2 * y) ≤ 120
d(x, y) = x + y ≤ 80
e(x, y) = x + (0.6 * y) ≤ 72