a(x) = x ≥ 0
b(y) = y ≥ 0
c(x, y) = y ≥ (-x) + 4
d(y) = y ≤ 7
e(x, y) = y ≤ (-x) + 10
p = 7000 (slider from 7000 to 9000, step 10)
f: (130 * x) + (235 * y) + 6690 = p