Question 206723
ways to select 6 bulbs out of 9 ___ 9C6 = 84


ways to select 2 d-bulbs out of 4 ___ 4C2 = 6


ways to select 4 t-bulbs out of 5 ___ 5C4 = 5


ways to select 2 d-bulbs and 4 t-bulbs ___ 6 * 5 = 30


probability of 2 d and 4 t ___ (30 / 84) = (15 / 41) = .366 (approx)