Question 1081927
The value of c can be determined.  We know that 3c+2c=0.5 and 5c=0.5, so c=0.1 and the probability of x=-1 is 0.3, x=9 is 0.2, x=1 is 0.4 and x=2 is 0.1
E(X)=-0.3+1.8+0.4+0.2=2.1
V(X)=(x-E(X))^2*p(x)
-3.1^2*0.3=2.883
6.9^2*0.2=9.522
1.1^2*0.4=4.84
0.1^2*0.1=0.001
They add to 17.246
sd is sqrt (V)=4.153