Calculation of central moments of an expression with symbolic values.

Does anybody know how we can calculate the mean, variance, skewness and kurtosis of the following expression:

1.0*b1 + b2*xi - b4*(- xi^3 + 3.0*xi) + b3*(xi^2 - 1.0)

Knowing that xi is a standard normal random variable(zero mean and std 1). bi's are coefficents, E[xi^k]=0 if k is odd, E[xi^0]=1, E[xi^2]=1, E[xi^4]=3, E[xi^6]=15.

I know that the matlab functions moment or mean or Kurtosis do not work here.

Thank you for your time.