T418

a = BarChart({1, 2, 3, 4}, {3 / 20, 7 / 20, 7 / 20, 3 / 20}, 0.02)
F(x) = (0 * (x < 1)) + (3 / 20 * (1 ≤ x < 2)) + (10 / 20 * (2 ≤ x < 3)) + (17 / 20 * (3 ≤ x < 4)) + (4 ≤ x)