a(x) = x ≤ 10
b(x) = x ≥ 50
c(y) = y ≤ 10
d(y) = y ≥ 50
e(x, y) = y ≥ (-x) + 90
f(x, y) = y ≤ (-x) + 50
g(x, y) = y ≤ (2 * x)
h(x, y) = y ≤ (-4 * x) + 100
i(x, y) = y ≥ (-1 / 2 * x) + 50