3. I. The variables X1, X2, X3 and Z1, Za are related in the following manner. Zi=(2X1+5X2-4X3)/7 Zz=(X1+2X2)/5 a Write down the above in vector-matrix notations. b Use part (a) to obtain the mean vector of Z, and Zz when E(X,)=1, E(X)=2 and E(X.)=-1. HI. Write down the following quadratic form in vector-matrix notation Xi'+2X2-+4X.'-5XX3