Question 1081926
E(X)=x*p(x)=-3c+18c+0.4+0.2=15c+0.6
However, we can solve for c initially
We know that the probability distribution has 0.5 accounted for, so 3c+2c=0.5
therefore, 5c=0.5
c=0.1
x=-1 with probability 0.3 and product -0.3
x=9 with probability 0.2 and product 1.8
x=1 with probability 0.4 and product 0.4
x=2 with probability 0.1 and product 0.2
E(X) is the sum or 2.1
This fits with c=0.1 above, since 15c+0.6=2.1