f(x) = 10 / (1 + 4 * ℯ^(-0.5 * x))
g(x) = 20 * exp(-0.5 * x) / (1 + 4 * exp(-0.5 * x))^(2)
h(x) = 80 * exp(-x) / (1 + 4 * exp(-0.5 * x))^(3) - 10 * exp(-0.5 * x) / (1 + 4 * exp(-0.5 * x))^(2)