Probability: A box contains ten objects which consists of 1 red ball, 2 white balls, 3 red cubes and 4 white cubes. Three objects are selected randoml

[CarolynKor]

A box contains ten objects which consists of 1 red ball, 2 white balls, 3 red cubes and 4
white cubes. Three objects are selected randomly without replacement from the box.
The events A and B are defined as follows:
A : Exactly two of the objects drawn are balls
B : Exactly one of the objects drawn is red in colour
Show that P(A) = 7/40 and find P(B) and P(A n B).

 

[Silver mist]

P(A) = 3/10×2/9×7/8×3
p(B) = 4/10×6/9×5/8×3
p(AnB) = 7/80