a box contain :

7white

3red

4black

and 6 green balls

if we choose 8 balls randomly without replacement . if selecting a white or a black ball is consider as wining >>>find :

(1) the probability that we get 6 wining balls

(2) the expected value for number of wining

my solutions:

(1)f(x)=

(11C6)*(9C2)\(20C8)

C: means combination

(2)

mean = 88\20