Question 1184400
A box contains 20 balls out which 7 are white balls, 5 are black balls, 6 are
red balls and 2 are yellow balls. If four balls are drawn at random. What is
the probability that balls of only <s>one two</s> colours and only three colours
are drawn?<pre>Notice that the "<s>one two</s>" doesn't make sense.

Edwin</pre>