f: x + y = 14
g: x + y = 18
h: (20 * x) + (32 * y) = 400
cost = 0 (slider from 0 to 15, step 0.05)
i: (0.7 * x) + (0.35 * y) = cost
time = 0 (slider from 0 to 200, step 1)
j: (3 * x) + (15 * y) = time