Let (X11,X12, ..., Xin). (X21, X22, ...,Xzn). .; (XmlXm2, "-,Xmn) represent m different observations of the vector ()1, 12. ... )n) of n variables. Define the matrix X by: X11 X12 Xin X21 X22 Xan X = Xml Xm2 I'mn Let 1 = (1,1, ..,1)' denote the m x 1 matrix whose elements all equal to 1. find the product of 1'X and interpret the result