In choosing what music to play at a charity fund raising event, Davon needs to have an equal number of string quartets from Mendelssohn, Schubert, and Rubinstein. If he is setting up a schedule of the 6 string quartets to be played, and he has 6 Mendelssohn, 15 Schubert, and 10 Rubinstein string quartets from which to choose, how many different schedules are possible