Question 984388
{{{P(R)=6/(6+5+4)=6/15=2/5}}}
{{{P(W)=5/15=1/3}}}
{{{P(B)=4/15}}}
So,
{{{E(X)=6*(2/5)+0*(1/3)-9(4/15)}}}
{{{E(X)=12/5-36/15}}}
{{{E(X)=36/15-36/15}}}
{{{E(X)=0}}}