18 to 24 months, 0, 0 to 3 months, 3 to 6 months, 4 to 6 months, 6 to 9 months, 9 to 12 months, 1 year, 12 to 18 months, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20