there r 2 w balls,3 b balls, 4R balls.In how many ways 3 balls can be selected s.t. atleast 1 b ball is there given that balls of same colors are distinct

 

ans is 64 i know how but what is wrong with my soln

³C₁* ⁸C₂    ( first selecting one black ball & then out of remaining  8 selecting 2 balls)

 

pls dont give a soln but tell mistake in my soln because we get 84 by calc this way