I want to create a distribution table and then find expected value,variance and standard deviation.

For example : X=-1,P(X)=0.2
                       X=0,P(X)=0.25
                       X=1,P(X)=0.35

                       X=2,P(X)=0.2

E(X) would then equal -1*0.2+0*0.25+1*0.35+2*0.2.

How can I do all of this with Maple ?